Add GitHub Actions build

.github/workflows/build.yml

@@ -0,0 +1,65 @@
+name: Build
+
+on: [push, pull_request, workflow_dispatch]
+
+env:
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: 1
+  DOTNET_NOLOGO: true
+  DOTNET_CLI_TELEMETRY_OPTOUT: 1
+  NuGetDirectory: ${{ github.workspace }}/nuget
+
+defaults:
+  run:
+    shell: pwsh
+
+jobs:
+  build:
+    name: ${{ matrix.platform.name }} ${{ matrix.dotnet.name }}
+    runs-on: ${{ matrix.platform.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        platform:
+        - { name: Windows x64, os: windows-2025 }
+        - { name: Ubuntu x64, os: ubuntu-24.04 }
+        - { name: macOS arm64, os: macos-15 }
+        dotnet:
+        - { name: .NET 8, version: '8.0.x' }
+        - { name: .NET 9, version: '9.0.x' }
+        - { name: .NET 10, version: '10.0.x' }
+
+    steps:
+    - name: Checkout HTML Renderer
+      uses: actions/checkout@v6
+
+    - name: Setup .NET ${{ matrix.dotnet.version }} SDK
+      id: setup-dotnet
+      uses: actions/setup-dotnet@v5
+      with:
+        dotnet-version: ${{ matrix.dotnet.version }}
+    - name: Enforce SDK Version
+      run: dotnet new globaljson --sdk-version ${{ steps.setup-dotnet.outputs.dotnet-version }} --force
+    - name: Verify SDK Installation
+      run: dotnet --info
+
+    - name: Restore Dependencies
+      run: dotnet restore Source/HtmlRenderer.sln
+
+    - name: Build
+      run: dotnet build Source/HtmlRenderer.sln --configuration Release --no-restore
+
+    - name: Create HtmlRenderer.Core NuGet package
+      run: dotnet pack Source/HtmlRenderer/HtmlRenderer.csproj --configuration Release --include-symbols -p:SymbolPackageFormat=snupkg --no-build --verbosity normal --output ${{ env.NuGetDirectory }}
+
+    - name: Create HtmlRenderer.WinForms NuGet package
+      run: dotnet pack Source/HtmlRenderer.WinForms/HtmlRenderer.WinForms.csproj --configuration Release --include-symbols -p:SymbolPackageFormat=snupkg --no-build --verbosity normal --output ${{ env.NuGetDirectory }}
+
+    - name: Create HtmlRenderer.WPF NuGet package
+      run: dotnet pack Source/HtmlRenderer.WPF/HtmlRenderer.WPF.csproj --configuration Release --include-symbols -p:SymbolPackageFormat=snupkg --no-build --verbosity normal --output ${{ env.NuGetDirectory }}
+
+    - name: Upload NuGet package artifacts
+      uses: actions/upload-artifact@v5
+      with:
+        name: "HTML Renderer (${{ matrix.platform.name }} ${{ matrix.dotnet.name }})"
+        path: ${{ env.NuGetDirectory }}/*.*nupkg