Close stale issue automatically (#530)

This will automatically close old issues and pull requests. It should be
fine to close those that have not received any responses.

.github/workflows/close-issue.yml

@@ -0,0 +1,26 @@
+# https://docs.github.com/en/actions/managing-issues-and-pull-requests/closing-inactive-issues
+# https://github.com/marketplace/actions/close-stale-issues
+name: Close inactive issues
+on:
+  schedule:
+    - cron: "30 1 * * *"
+
+jobs:
+  close-issues:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/stale@v8
+        with:
+          days-before-issue-stale: 14
+          days-before-issue-close: 0
+          stale-issue-label: "no-activity"
+          close-issue-message: "This issue was closed because it has been inactive for 14 days."
+          exempt-issue-labels: "bug,enhancement,keep"
+          days-before-pr-stale: -1
+          days-before-pr-close: 14
+          stale-pr-label: "no-activity"
+          close-pr-message: "This pull request was closed because it has been inactive for 14 days. Please reopen if you still intend to submit this pull request."
+          repo-token: ${{ secrets.GITHUB_TOKEN }}