chore(label-actions): add auto:inactivity-pr-close (#28896)

.github/label-actions.yml

@@ -225,6 +225,21 @@
     This Issue will now be closed and locked. We may later batch-delete this issue. This way we keep Issues actionable, and free of duplicates or wrong bug reports.
 
 
+    Thanks, the Renovate team
+  close: true
+  close-reason: 'not planned'
+
+'auto:inactivity-pr-close':
+  comment: >
+    **This PR has been closed due to inactivity, but resuming work on it in future would be welcome.**
+
+
+    We try to avoid having too many PRs open at once, so we close PRs that have been inactive for too long or which don't seem on track to be mergeable.
+
+
+    If you want to continue working on this PR, please reopen it and let us know.
+
+
     Thanks, the Renovate team
   close: true
   close-reason: 'not planned'