Add stale label to stale PRs

Author: mcculls

.github/workflows/prune-old-pull-requests.yaml

@@ -19,4 +19,4 @@ jobs:
           days-before-pr-stale: 90 # Only enable stale bot for PRs with no activity for 90 days
           stale-pr-message: 'This pull request has been marked as stale because it has not had activity over the past quarter. It will be closed in 7 days if no further activity occurs. Feel free to reopen the PR if you are still working on it.'
           close-pr-message: 'This pull request has been closed because it has not had activity over the past quarter. Feel free to reopen the PR if you are still working on it.'
-          stale-pr-label: 'tag: stale'
+          stale-pr-label: 'stale'