feat: Add documentation build and deployment workflow

.github/workflows/docs.yml

@@ -0,0 +1,46 @@
+name: Docs
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - 'docs/**'
+      - 'src/**'
+
+permissions:
+  contents: write
+
+jobs:
+  build-deploy:
+    name: Build & Deploy Docs
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET 10
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Cache NuGet packages
+        uses: actions/cache@v4
+        with:
+          path: ~/.nuget/packages
+          key: nuget-${{ runner.os }}-${{ hashFiles('src/**/*.csproj') }}
+          restore-keys: nuget-${{ runner.os }}-
+
+      - name: Restore .NET tools
+        run: dotnet tool restore
+
+      - name: Build solution
+        run: dotnet build src/EchoHub.slnx --configuration Release
+
+      - name: Generate documentation
+        run: dotnet docfx docs/docfx.json
+
+      - name: Deploy to web branch
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./docs/_site
+          publish_branch: web