Add stale action

.github/workflows/stale.yaml

@@ -0,0 +1,40 @@
+name: 'Close stale issues and PRs'
+on:
+  schedule:
+    - cron: '30 1 * * *'
+  workflow_dispatch:
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          days-before-stale: 30
+          days-before-close: 5
+          stale-issue-label: "stale"
+          exempt-issue-labels: "no-stale,help-wanted"
+          stale-pr-label: "stale"
+          exempt-pr-labels: "no-stale"
+          stale-issue-message: >
+            There hasn't been any activity on this issue recently. To keep the
+            number of open issues under control, we have to clean some of the
+            old issues, as many of them have already been resolved with the
+            latest updates.
+
+            Please make sure to update to the latest WaterSmart version and
+            check if that solves the issue. Let us know if that works for you by
+            adding a comment 👍
+
+            This issue has now been marked as stale and will be closed if no
+            further activity occurs. Thank you for your contributions.
+          stale-pr-message: >
+            There hasn't been any activity on this pull request recently. This
+            pull request has been automatically marked as stale because of that
+            and will be closed if no further activity occurs within 7 days.
+
+            If you are the author of this PR, please leave a comment if you want
+            to keep it open. Also, please rebase your PR onto the latest dev
+            branch to ensure that it's up to date with the latest changes.
+
+            Thank you for your contribution!