chore: add comment

Author: jenstroeger

.github/workflows/pr-change-set.yaml

@@ -14,7 +14,8 @@ on:
 permissions:
   contents: read
 
-# https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#concurrency
+# Cancel existing running workflows for a PR when a new change is pushed
+# to that PR. See also: https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#concurrency
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true