chore: beef up CI

Author: buenos-nachos

…hub/workflows/validate-readme-files.yaml .github/workflows/ci.yaml.github/workflows/validate-readme-files.yaml renamed to .github/workflows/ci.yaml .github/workflows/validate-readme-files.yaml renamed to .github/workflows/ci.yaml

@@ -1,8 +1,11 @@
-name: Validate README files
+name: CI
 on:
   pull_request:
-    branches:
-      - main
+    branches: [main]
+# Cancel in-progress runs for pull requests when developers push new changes
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
 jobs:
   validate-contributors:
     runs-on: ubuntu-latest