adds more dotnet installs to CI

Author: TheAngryByrd

.github/workflows/build.yml

@@ -19,10 +19,14 @@ jobs:
       uses: actions/setup-dotnet@v1
       with:
         dotnet-version: '3.1.x'
+    - name: Use .NET Core 5.x SDK
+      uses: actions/setup-dotnet@v1
+      with:
+        dotnet-version: '5.0.x'
     # Not specifying a version will attempt to install via global.json
     - name: Use .NET Core global.json
       uses: actions/setup-dotnet@v1
-
+        
     - name: Build
       if: runner.os != 'Windows'
       run: |