ci: add .NET 9 preview test pipeline

.github/workflows/net-preview.yml

@@ -0,0 +1,28 @@
+on:
+  pull_request:
+
+name: net-preview
+env:
+  DOTNET_CLI_TELEMETRY_OPTOUT: true
+  DOTNET_NOLOGO: true
+  dotnet-version: 9.0.0-preview.7.24405.2
+  dotnet-target: net9.0
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      # Setup
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: ${{ env.dotnet-version }}
+
+      - run: dotnet --info
+
+      # Checkout
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      # Run all tests
+      - run: dotnet test -c Release -f ${{ env.dotnet-target }} -p:NetPreview=true