Update CI for .NET 6

Author: EraYaN

.github/workflows/build-test.yaml

@@ -20,7 +20,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v1
         with:
-          dotnet-version: 5.0.x
+          dotnet-version: 6.0.x
 
       - name: Restore dependencies
         run: dotnet restore