Update build-test-deploy.yml

Author: BenjaminMichaelis

.github/workflows/build-test-deploy.yml

@@ -21,7 +21,9 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v2
       with:
-        dotnet-version: 6.0.x
+        dotnet-version: | 
+            3.1.x
+            6.x
     - name: Restore dependencies
       run: dotnet restore
     - name: Set Version