docs(docs_v2): Add docusaurus as per #468

docs_v2/.gitignore

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+# Dependencies
+/node_modules
+
+# Production
+/build
+
+# Generated files
+.docusaurus
+.cache-loader
+
+# Misc
+.DS_Store
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*

docs_v2/README.md

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+# Website
+
+This website is built using [Docusaurus](https://docusaurus.io/), a modern static website generator.
+
+### Installation
+
+```
+$ yarn
+```
+
+### Local Development
+
+```
+$ yarn start
+```
+
+This command starts a local development server and opens up a browser window. Most changes are reflected live without having to restart the server.
+
+### Build
+
+```
+$ yarn build
+```
+
+This command generates static content into the `build` directory and can be served using any static contents hosting service.
+
+### Deployment
+
+Using SSH:
+
+```
+$ USE_SSH=true yarn deploy
+```
+
+Not using SSH:
+
+```
+$ GIT_USER=<Your GitHub username> yarn deploy
+```
+
+If you are using GitHub pages for hosting, this command is a convenient way to build the website and push to the `gh-pages` branch.

docs_v2/babel.config.js

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+module.exports = {
+  presets: [require.resolve('@docusaurus/core/lib/babel/preset')],
+};

docs_v2/blog/2019-05-28-first-blog-post.md

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+---
+slug: first-blog-post
+title: First Blog Post
+authors:
+  name: Gao Wei
+  title: Docusaurus Core Team
+  url: https://github.com/wgao19
+  image_url: https://github.com/wgao19.png
+tags: [hola, docusaurus]
+---
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet

docs_v2/blog/2019-05-29-long-blog-post.md

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+---
+slug: long-blog-post
+title: Long Blog Post
+authors: endi
+tags: [hello, docusaurus]
+---
+
+This is the summary of a very long blog post,
+
+Use a `<!--` `truncate` `-->` comment to limit blog post size in the list view.
+
+<!--truncate-->
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque elementum dignissim ultricies. Fusce rhoncus ipsum tempor eros aliquam consequat. Lorem ipsum dolor sit amet

docs_v2/blog/2021-08-01-mdx-blog-post.mdx

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+---
+slug: mdx-blog-post
+title: MDX Blog Post
+authors: [slorber]
+tags: [docusaurus]
+---
+
+Blog posts support [Docusaurus Markdown features](https://docusaurus.io/docs/markdown-features), such as [MDX](https://mdxjs.com/).
+
+:::tip
+
+Use the power of React to create interactive blog posts.
+
+```js
+<button onClick={() => alert('button clicked!')}>Click me!</button>
+```
+
+<button onClick={() => alert('button clicked!')}>Click me!</button>
+
+:::

docs_v2/blog/2021-08-26-welcome/index.md

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+---
+slug: welcome
+title: Welcome
+authors: [slorber, yangshun]
+tags: [facebook, hello, docusaurus]
+---
+
+[Docusaurus blogging features](https://docusaurus.io/docs/blog) are powered by the [blog plugin](https://docusaurus.io/docs/api/plugins/@docusaurus/plugin-content-blog).
+
+Simply add Markdown files (or folders) to the `blog` directory.
+
+Regular blog authors can be added to `authors.yml`.
+
+The blog post date can be extracted from filenames, such as:
+
+- `2019-05-30-welcome.md`
+- `2019-05-30-welcome/index.md`
+
+A blog post folder can be convenient to co-locate blog post images:
+
+![Docusaurus Plushie](./docusaurus-plushie-banner.jpeg)
+
+The blog supports tags as well!
+
+**And if you don't want a blog**: just delete this directory, and use `blog: false` in your Docusaurus config.

docs_v2/blog/authors.yml

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+endi:
+  name: Endilie Yacop Sucipto
+  title: Maintainer of Docusaurus
+  url: https://github.com/endiliey
+  image_url: https://github.com/endiliey.png
+
+yangshun:
+  name: Yangshun Tay
+  title: Front End Engineer @ Facebook
+  url: https://github.com/yangshun
+  image_url: https://github.com/yangshun.png
+
+slorber:
+  name: Sébastien Lorber
+  title: Docusaurus maintainer
+  url: https://sebastienlorber.com
+  image_url: https://github.com/slorber.png

docs_v2/blog/tags.yml

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+facebook:
+  label: Facebook
+  permalink: /facebook
+  description: Facebook tag description
+hello:
+  label: Hello
+  permalink: /hello
+  description: Hello tag description
+docusaurus:
+  label: Docusaurus
+  permalink: /docusaurus
+  description: Docusaurus tag description
+hola:
+  label: Hola
+  permalink: /hola
+  description: Hola tag description

docs_v2/docs/01-intro.md

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+---
+sidebar_position: 0
+sidebar_class_name: hidden
+---
+
+# Introduction
+
+Build Dart/Flutter applications powered by Large Language Models. 
+
+## What is LangChain.dart?
+
+LangChain.dart is an unofficial Dart port of the popular [LangChain](https://github.com/hwchase17/langchain) Python framework created by [Harrison Chase](https://www.linkedin.com/in/harrison-chase-961287118). LangChain is a framework for developing applications that are powered by large language models (LLMs).
+
+It comes with a set of components that make working with LLMs easy. 
+The components can be grouped into a few core modules:
+
+![LangChain.dart](https://raw.githubusercontent.com/davidmigloz/langchain_dart/main/docs/img/langchain.dart.png)
+
+- 📃 **Model I/O:** LangChain offers a unified API for interacting with various LLM providers (e.g. OpenAI, Google, Mistral, Ollama, etc.), allowing developers to switch between them with ease. Additionally, it provides tools for managing model inputs (prompt templates and example selectors) and parsing the resulting model outputs (output parsers).
+- 📚 **Retrieval:** assists in loading user data (via document loaders), transforming it (with text splitters), extracting its meaning (using embedding models), storing (in vector stores) and retrieving it (through retrievers) so that it can be used to ground the model's responses (i.e. Retrieval-Augmented Generation or RAG). 
+- 🤖 **Agents:** "bots" that leverage LLMs to make informed decisions about which available tools (such as web search, calculators, database lookup, etc.) to use to accomplish the designated task.
+
+The different components can be composed together using the [LangChain Expression Language (LCEL)](https://langchaindart.dev/#/expression_language/get_started).
+
+## Motivation
+
+Large Language Models (LLMs) have revolutionized Natural Language Processing (NLP), serving as essential components in a wide range of applications, such as question-answering, summarization, translation, and text generation.
+
+The adoption of LLMs is creating a new tech stack in its wake. However, emerging libraries and tools are predominantly being developed for the Python and JavaScript ecosystems. As a result, the number of applications leveraging LLMs in these ecosystems has grown exponentially.
+
+In contrast, the Dart / Flutter ecosystem has not experienced similar growth, which can likely be attributed to the scarcity of Dart and Flutter libraries that streamline the complexities associated with working with LLMs.
+
+LangChain.dart aims to fill this gap by abstracting the intricacies of working with LLMs in Dart and Flutter, enabling developers to harness their combined potential effectively.
+
+## Packages
+
+LangChain.dart has a modular design that allows developers to import only the components they need. The ecosystem consists of several packages:
+
+### [`langchain_core`](https://pub.dev/packages/langchain_core)
+
+Contains only the core abstractions as well as LangChain Expression Language as a way to compose them together. 
+
+> Depend on this package to build frameworks on top of LangChain.dart or to interoperate with it.
+
+### [`langchain`](https://pub.dev/packages/langchain)
+
+Contains higher-level and use-case specific chains, agents, and retrieval algorithms that are at the core of the application's cognitive architecture.
+
+> Depend on this package to build LLM applications with LangChain.dart.  
+> 
+> This package exposes `langchain_core` so you don't need to depend on it explicitly.
+
+### [`langchain_community`](https://pub.dev/packages/langchain_community)
+
+Contains third-party integrations and community-contributed components that are not part of the core LangChain.dart API.
+
+> Depend on this package if you want to use any of the integrations or components it provides.
+
+### Integration-specific packages
+
+Popular third-party integrations (e.g. [`langchain_openai`](https://pub.dev/packages/langchain_openai), [`langchain_google`](https://pub.dev/packages/langchain_google), [`langchain_ollama`](https://pub.dev/packages/langchain_ollama), etc.) are moved to their own packages so that they can be imported independently without depending on the entire `langchain_community` package.
+
+> Depend on an integration-specific package if you want to use the specific integration.
+
+
+## Getting started
+
+To start using LangChain.dart, add `langchain` as a dependency to your `pubspec.yaml` file. Also, include the dependencies for the specific integrations you want to use (e.g.`langchain_community`, `langchain_openai`, `langchain_google`, etc.):
+
+```yaml
+dependencies:
+  langchain: {version}
+  langchain_community: {version}
+  langchain_openai: {version}
+  langchain_google: {version}
+  ...
+```
+
+The most basic building block of LangChain.dart is calling an LLM on some prompt. LangChain.dart provides a unified interface for calling different LLMs. For example, we can use `ChatGoogleGenerativeAI` to call Google's Gemini model:
+
+```dart
+final model = ChatGoogleGenerativeAI(apiKey: googleApiKey);
+final prompt = PromptValue.string('Hello world!');
+final result = await model.invoke(prompt);
+// Hello everyone! I'm new here and excited to be part of this community.
+```
+
+But the power of LangChain.dart comes from chaining together multiple components to implement complex use cases. For example, a RAG (Retrieval-Augmented Generation) pipeline that would accept a user query, retrieve relevant documents from a vector store, format them using prompt templates, invoke the model, and parse the output:
+
+```dart
+// 1. Create a vector store and add documents to it
+final vectorStore = MemoryVectorStore(
+  embeddings: OpenAIEmbeddings(apiKey: openaiApiKey),
+);
+await vectorStore.addDocuments(
+  documents: [
+    Document(pageContent: 'LangChain was created by Harrison'),
+    Document(pageContent: 'David ported LangChain to Dart in LangChain.dart'),
+  ],
+);
+
+// 2. Define the retrieval chain
+final retriever = vectorStore.asRetriever();
+final setupAndRetrieval = Runnable.fromMap<String>({
+  'context': retriever.pipe(
+    Runnable.mapInput((docs) => docs.map((d) => d.pageContent).join('\n')),
+  ),
+  'question': Runnable.passthrough(),
+});
+
+// 3. Construct a RAG prompt template
+final promptTemplate = ChatPromptTemplate.fromTemplates([
+  (ChatMessageType.system, 'Answer the question based on only the following context:\n{context}'),
+  (ChatMessageType.human, '{question}'),
+]);
+
+// 4. Define the final chain
+final model = ChatOpenAI(apiKey: openaiApiKey);
+const outputParser = StringOutputParser<ChatResult>();
+final chain = setupAndRetrieval
+    .pipe(promptTemplate)
+    .pipe(model)
+    .pipe(outputParser);
+
+// 5. Run the pipeline
+final res = await chain.invoke('Who created LangChain.dart?');
+print(res);
+// David created LangChain.dart
+```
+
+## Documentation
+
+- [LangChain.dart documentation](https://langchaindart.dev)
+- [Sample apps](https://github.com/davidmigloz/langchain_dart/tree/main/examples)
+- [LangChain.dart blog](https://blog.langchaindart.dev)
+- [Project board](https://github.com/users/davidmigloz/projects/2/views/1)
+
+## Community
+
+Stay up-to-date on the latest news and updates on the field, have great discussions, and get help in the official [LangChain.dart Discord server](https://discord.gg/x4qbhqecVR).
+
+[![LangChain.dart Discord server](https://invidget.switchblade.xyz/x4qbhqecVR?theme=light)](https://discord.gg/x4qbhqecVR)
+
+## Contribute
+
+| 📢 **Call for Collaborators** 📢                                        |
+|-------------------------------------------------------------------------|
+| We are looking for collaborators to join the core group of maintainers. |
+
+New contributors welcome! Check out our [Contributors Guide](https://github.com/davidmigloz/langchain_dart/blob/main/CONTRIBUTING.md) for help getting started.
+
+Join us on [Discord](https://discord.gg/x4qbhqecVR) to meet other maintainers. We'll help you get your first contribution in no time!
+
+## Related projects
+
+- [LangChain](https://github.com/langchain-ai/langchain): The original Python LangChain project.
+- [LangChain.js](https://github.com/langchain-ai/langchainjs): A JavaScript port of LangChain.
+- [LangChain.go](https://github.com/tmc/langchaingo): A Go port of LangChain.
+- [LangChain.rb](https://github.com/andreibondarev/langchainrb): A Ruby port of LangChain.
+
+## Sponsors
+
+<p align="center">
+  <a href="https://github.com/sponsors/davidmigloz">
+    <img src='https://raw.githubusercontent.com/davidmigloz/sponsors/main/sponsors.svg'/>
+  </a>
+</p>
+
+## License
+
+LangChain.dart is licensed under the [MIT License](https://github.com/davidmigloz/langchain_dart/blob/main/LICENSE).

docs_v2/docs/02-tutorials/01-llm_chain.md

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+---
+sidebar_position: 0
+sidebar_class_name: hidden
+---
+
+
+# Build a Simple LLM Application with LCEL