Add stale PR workflow using actions/stale

.github/workflows/stale.yml

@@ -0,0 +1,29 @@
+# https://github.com/actions/stale
+
+name: "Close Stale PRs"
+on:
+  schedule:
+    - cron: '0 0 * * *'
+  workflow_dispatch:
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - uses: actions/stale@v9
+        with:
+          days-before-pr-stale: 15
+          days-before-pr-close: 3
+          stale-pr-label: 'Inactive'
+          exempt-draft-pr: true
+          days-before-issue-stale: -1
+          days-before-issue-close: -1
+          stale-pr-message: |
+            This pull request is being marked as inactive because of no recent activity.
+            If your PR hasn't been reviewed yet, please ensure it follows the [contribution guidelines](https://github.com/frappe/frappe-ui/blob/main/CONTRIBUTING.md).
+
+            It will be closed in 3 days if no further activity occurs.
+            Thank you for contributing!
+          labels-to-remove-when-unstale: 'Inactive'