docs: Add README (#41)

* docs: Add README

* Add Blogs

README.md

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+# ScalaTest OpenTelemetry Reporter
+
+[ScalaTest](https://www.scalatest.org/) extension that instruments your tests with [OpenTelemetry](https://opentelemetry.io/).
+
+## Getting Started
+
+This example demonstrates how to send trace data to [Jaeger](https://www.jaegertracing.io/) in localhost.
+
+Before you start, you need to run Jaeger in a Docker container.
+
+```yaml
+services:
+  jeager:
+    image: jaegertracing/all-in-one:latest
+    ports:
+      - "4317:4317"
+      - "16686:16686"
+```
+
+```shell
+docker compose up -d
+```
+
+Add the following configuration to your `build.sbt`.
+
+```scala
+lazy val `my-project` = (project in file("my-project"))
+  .settings(
+    // Add dependencies
+    libraryDependencies ++= Seq(
+      "org.scalatest"           %% "scalatest"                   % "3.2.18"       % Test,
+      "io.opentelemetry"         % "opentelemetry-sdk"           % "1.38.0"       % Test,
+      "io.opentelemetry"         % "opentelemetry-exporter-otlp" % "1.38.0"       % Test,
+      "io.opentelemetry.semconv" % "opentelemetry-semconv"       % "1.21.0-alpha" % Test,
+      "dev.nomadblacky"         %% "scalatest-otel-reporter"     % "0.2.0-alpha"  % Test,
+    ),
+    // Add the reporter class
+    Test / testOptions += Tests.Argument(
+      TestFrameworks.ScalaTest,
+      "-C",
+      "example.JaegerTestReporter",
+    ),
+  )
+```
+
+Create a reporter class that extends `OpenTelemetryTestReporter` and implements the `otel` method.  
+Below is an example of sending trace data to Jaeger in localhost.
+
+```scala
+package example
+
+import dev.nomadblacky.scalatest_otel_reporter.OpenTelemetryTestReporter
+import io.opentelemetry.api.OpenTelemetry
+import io.opentelemetry.api.common.Attributes
+import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter
+import io.opentelemetry.sdk.OpenTelemetrySdk
+import io.opentelemetry.sdk.resources.Resource
+import io.opentelemetry.sdk.trace.SdkTracerProvider
+import io.opentelemetry.sdk.trace.`export`.BatchSpanProcessor
+import io.opentelemetry.semconv.ResourceAttributes
+
+import java.util.concurrent.TimeUnit
+
+// Mix-In OpenTelemetryTestReporter
+class JaegerTestReporter extends OpenTelemetryTestReporter {
+  def otel: OpenTelemetry = {
+    // Direct trace data to Jaeger on localhost
+    val jaegerOtlpExporter =
+      OtlpGrpcSpanExporter.builder.setEndpoint("http://localhost:4317").setTimeout(30, TimeUnit.SECONDS).build
+
+    // Configure the service name (recommended)
+    val serviceNameResource =
+      Resource.create(Attributes.of(ResourceAttributes.SERVICE_NAME, "scalatest-otel-demo-manual"))
+
+    // Configure the SpanProcessor
+    val tracerProvider = SdkTracerProvider.builder
+      .addSpanProcessor(BatchSpanProcessor.builder(jaegerOtlpExporter).build)
+      .setResource(Resource.getDefault.merge(serviceNameResource))
+      .build
+
+    // Return OpenTelemetry instance
+    OpenTelemetrySdk.builder.setTracerProvider(tracerProvider).build
+  }
+}
+```
+
+Implement the test as usual.
+
+```scala
+package example
+
+import org.scalatest.funsuite.AnyFunSuiteLike
+
+class SimpleTests extends AnyFunSuiteLike {
+  test("sum") {
+    assert(1 + 1 == 2)
+  }
+  test("sub") {
+    assert(1 - 1 == 0)
+  }
+}
+
+class FailedTests extends AnyFunSuiteLike {
+  test("failed assertion") {
+    assert(1 + 1 == 3)
+  }
+  test("throw an exception") {
+    throw new RuntimeException("An exception occurred")
+  }
+}
+// ...
+```
+
+Execute the test in the sbt shell.
+
+```shell
+sbt
+> my-project/test
+```
+
+Open the Jaeger UI in your browser (http://localhost:16686/) and you will see the trace data.
+
+
+![img.png](jaeger-trace.png)
+
+## Blogs
+
+- [テストでも Observability したいっ！ ScalaTest を OpenTelemetry で計装してみた (ScalaMatsuri 2024 Unconference)](https://cobalt-lupin-e48.notion.site/Observability-ScalaTest-OpenTelemetry-b2d3e69d75f146b1a26fe9199d51e3e9)