Add piper example

[PeterD1524]

I am working on LFX Workspace: Support piper as a new backend of the WASI-NN WasmEdge plugin #3483.
This PR adds a basic example of using the plugin to perform text-to-speech.

[juntao]

Hello, I am a code review bot on flows.network. Here are my reviews of code commits in this PR.

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Commit b3c64f2a2acf2a758c4451f7f54f93ca05689a92

Key Changes:

1. Added a new Cargo.toml file with dependencies on serde_json and wasmedge-wasi-nn.
2. Added a new README.md file with instructions on how to use the WasmEdge WASI-NN Piper plugin for Text-to-Speech (TTS).
3. Added a new main.rs file with Rust code for creating a TTS graph using the WasmEdge WASI-NN Piper plugin.

Potential Problems:

1. The patch seems to add a lot of new functionality related to Text-to-Speech using the WasmEdge WASI-NN Piper plugin without mentioning any specific issues or bugs. It would be helpful to have clear information on the purpose of these changes and if they are solving a particular problem or adding new features.
2. The patch introduces new dependencies like serde_json and wasmedge-wasi-nn. It is essential to ensure that these dependencies are necessary and do not introduce security vulnerabilities or conflicts with existing dependencies.
3. The patch adds complex build and execution instructions in the README.md file. It is important to verify the accuracy and completeness of these instructions to ensure that users can successfully build and execute the project.
4. The main.rs code adds functionality for TTS using the WasmEdge WASI-NN Piper plugin. It is crucial to review the code for performance optimizations, error handling, and best practices in Rust programming.
5. The patch includes external links for model download and additional resources. It is important to ensure that these links are valid, secure, and relevant to the project.

Overall, the patch introduces significant changes related to TTS functionality using the WasmEdge WASI-NN Piper plugin. Reviewing the code, dependencies, instructions, and external resources thoroughly will be crucial to ensure the quality and reliability of the added functionality.

[hydai]

LGTM. @dm4 PTAL

[dm4]

Could you please help add the following items? Thank you!

1. Provide a simple explanation of the related dependency installation in the README.md, such as libespeak-ng, libonnxruntime, libpiper, etc.
2. Add a GitHub workflow in .github/workflows/piper.yml to ensure that the example can run successfully.

[PeterD1524]

@dm4 I have added the following items.

1. Provide a simple explanation of the related dependency installation in the README.md, such as libespeak-ng, libonnxruntime, libpiper, etc.

075409e

2. Add a GitHub workflow in .github/workflows/piper.yml to ensure that the example can run successfully.

870e600

[hydai]

LGTM. @dm4 PTAL.