reactivated stale.yaml as github action (#3577)

The old `stale.yaml` seems not to work anymore, so I set up the same
content in a new github workflow.

I think we should use it again to get rid of old issues.

.github/stale.yaml

@@ -1,19 +0,0 @@
-# Number of days of inactivity before an issue becomes stale
-daysUntilStale: 60
-# Number of days of inactivity before a stale issue is closed
-daysUntilClose: 7
-# Issues with these labels will never be considered stale
-exemptLabels:
-  - pinned
-  - security
-  - under investigation
-  - pr welcome
-# Label to use when marking an issue as stale
-staleLabel: wontfix
-# Comment to post when marking an issue as stale. Set to `false` to disable
-markComment: >
-  This issue has been automatically marked as stale because it has not had
-  recent activity. It will be closed if no further activity occurs. Thank you
-  for your contributions.
-# Comment to post when closing a stale issue. Set to `false` to disable
-closeComment: false

.github/workflows/stale.yaml

@@ -0,0 +1,20 @@
+name: "Close stale issues and PRs"
+
+on:
+  schedule:
+    - cron: "30 1 * * 6" # every Saturday at 1:30
+
+permissions:
+  issues: write
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          stale-issue-message: "This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions."
+          days-before-issue-stale: 60
+          days-before-issue-close: 7
+          stale-issue-label: "wontfix"
+          exempt-issue-labels: "pinned,security,under investigation,pr welcome"