Maintenance: Reactivate stale workflow. (#410)

.github/workflows/stale.yml

@@ -0,0 +1,31 @@
+# This workflow warns and then closes issues and PRs that have had no activity for a specified amount of time.
+#
+# You can adjust the behavior by modifying this file.
+# For more information, see:
+# https://github.com/actions/stale
+name: Mark stale issues and pull requests
+
+permissions: read-all
+
+on:
+  schedule:
+  - cron: '15 5 * * *'
+
+jobs:
+  stale:
+
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+
+    steps:
+    - uses: actions/stale@v8
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        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.'
+        stale-pr-message: 'This PR 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.'
+        stale-issue-label: 'stale'
+        stale-pr-label: 'stale'
+        exempt-issue-labels: 'pinned'
+        exempt-pr-labels: 'pinned'