ci: use reusable stale bot workflow (#314)

Author: jooola

.github/workflows/stale.yml

@@ -4,21 +4,10 @@ on:
   schedule:
     - cron: "30 12 * * *"
 
-permissions:
-  issues: write
-  pull-requests: write
-
 jobs:
   stale:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/stale@v8
-        with:
-          stale-issue-message: "This issue has been marked as stale because it has not had recent activity. The bot will close the issue if no further action occurs."
-          exempt-issue-labels: "pinned"
-          stale-issue-labels: "stale"
-          stale-pr-message: "This PR has been marked as stale because it has not had recent activity. The bot will close the PR if no further action occurs."
-          exempt-pr-labels: "pinned"
-          stale-pr-labels: "stale"
-          days-before-stale: 90
-          days-before-close: 30
+    permissions:
+      issues: write
+      pull-requests: write
+
+    uses: hetznercloud/.github/.github/workflows/stale.yml@main