update build actions for .net8

Author: brockallen

.github/workflows/ci.yml

@@ -16,6 +16,7 @@ on:
 env:
   AZURE_WEBAPP_NAME: DuendeSoftware-Demo       # set this to your application's name
   AZURE_WEBAPP_PACKAGE_PATH: './publish'      # set this to the path to your web app project, defaults to the repository root
+  DOTNET_VERSION: '8.0.x'                     # set this to the dot net version to use
 
 jobs:
   build-and-deploy:
@@ -28,6 +29,8 @@ jobs:
       # Setup .NET Core SDK
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v1
+        with:
+          dotnet-version: ${{ env.DOTNET_VERSION }} 
 
       # Run dotnet build and publish
       - name: dotnet build and publish