Update verify-dotnet.ps1

.github/workflows/test-dotnet.yml

@@ -18,7 +18,7 @@ jobs:
       fail-fast: false
       matrix:
         operating-system: [ubuntu-latest, windows-latest, macOS-latest]
-        dotnet-version: ['2.1', '2.2', '3.0', '3.1', '5.0', '6.0', '7.0']
+        dotnet-version: ['2.1', '2.2', '3.0', '3.1', '5.0', '6.0', '7.0', '8.0']
     steps:
       - name: Checkout
         uses: actions/checkout@v3