ci: Cancel workflows in progress on new push to PR (#1679)

This ensures only one instance of the workflow is running per PR by
canceling any previous runs of the workflow.

Co-authored-by: Matthew Wear <matthew.wear@gmail.com>

.github/workflows/ci.yml

@@ -9,6 +9,10 @@ on:
     branches:
       - main
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}  # Ensure that only one instance of this workflow is running per Pull Request
+  cancel-in-progress: true  # Cancel any previous runs of this workflow
+
 jobs:
   base:
     strategy: