run the stale issues bot on demand

Author: Christopher Doris

.github/workflows/stale.yaml

@@ -1,7 +1,8 @@
-name: 'Close stale issues and PRs'
+name: 'Stale issues and PRs'
 on:
   schedule:
     - cron: '30 1 * * *'
+  workflow_dispatch:
 permissions:
   issues: write
   pull-requests: write