chore: Cancel workflow if no longer needed

Author: jcs090218

Diff for: .github/workflows/test.yml

@@ -7,6 +7,10 @@ on:
     branches: [ "master" ]
   workflow_dispatch:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 env:
   Solution_Name: shader-ls.sln