Use dotnet 8

Author: kblok

.github/workflows/PushNugetPackageToNugetOrg.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v3
       with:
-        dotnet-version: 6.0.x
+        dotnet-version: 8.0.x
     - name: Install dependencies
       run: |
         dotnet restore lib/PuppeteerSharp.sln