Ensure both net 3.1 and 6.0 SDKs are installed on build agent

Author: sandermvanvliet

.github/workflows/dotnet.yml

@@ -16,7 +16,9 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 6.0.x
+        dotnet-version: |
+          3.1.x
+          6.0.x
     - name: Restore dependencies
       run: dotnet restore
     - name: Build

.github/workflows/release.yml

@@ -19,7 +19,9 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 6.0.x
+        dotnet-version: |
+          3.1.x
+          6.0.x
     - name: Restore dependencies
       run: dotnet restore
     - name: Build