run .NET Framework tests on windows

ubuntu image no longer comes with mono pre-installed. installing it is easy, but running .NET Framework tests on windows in parallel is probably faster

.github/workflows/ci.yml

@@ -9,21 +9,25 @@ on:
 
 jobs:
   build_test:
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+        framework: [net6.0, net481, net461]
+    runs-on: ${{ matrix.os }}
     steps:
-    - name: Checkout
-      uses: actions/checkout@v4
+      - name: Checkout
+        uses: actions/checkout@v4
 
-    - name: Setup .NET
-      uses: actions/setup-dotnet@v4
-      with:
-        dotnet-version: 6.0.x
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: |
+            6.0.x
+            4.8.1
+            4.6.1
 
-    - name: Restore dependencies
-      run: dotnet restore
+      - name: Restore dependencies
+        run: dotnet restore
 
-    - name: Build
-      run: dotnet build -c Release --no-restore
-
-    - name: Test
-      run: dotnet test --no-build -c Release /p:CollectCoverage=true /p:Threshold=80 /p:Include=\"[Flurl]*,[Flurl.Http]*,[Flurl.Http.Newtonsoft]*\" /p:Exclude="[*]*.GeneratedExtensions"
+      - name: Test
+        run: dotnet test --framework ${{ matrix.framework }} -c Release /p:CollectCoverage=true /p:Threshold=80 /p:Include=\"[Flurl]*,[Flurl.Http]*,[Flurl.Http.Newtonsoft]*\" /p:Exclude="[*]*.GeneratedExtensions"