(build) Install required .NET Version

This will be required until we move off of .NET 5.0.

Author: gep13

.github/workflows/build.yml

@@ -26,6 +26,11 @@ jobs:
       - name: Fetch all tags and branches
         run: git fetch --prune --unshallow
 
+      - name: Install .NET SDK 5.0.x
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '5.0.x'
+
       - name: Cache Tools
         uses: actions/cache@v2
         with: