docs: stale PR response

Author: samuelmaddock

Diff for: playbooks/responses/stale-pr.md

@@ -0,0 +1,19 @@
+---
+action:
+ - add 'stale' label
+ - close pull request
+---
+
+Thank you for your contribution to the project!
+
+We apologize for the delay in reviewing your pull request. In the time since it
+was opened, there have been many changes to the codebase, and it's possible that
+your pull request is no longer applicable or conflicts with more recent updates.
+
+To keep pull requests relevant to maintainers, we'll be closing this pull
+request for now. However, if you believe the pull request is still relevant or
+if there was a mistake, feel free to request us to reopen it or provide a
+follow-up comment.
+
+If you wish to continue pursuing your contribution, please update your branch
+with the latest changes on `main` and resolve any existing conflicts.