github actions: Add stale workflow

kpatch maintainers have limited time.  While we greatly appreciate all
of our contributors, unfortunately it's not uncommon for kpatch issues
and PRs to get ignored for years.

Add a github workflow which marks issues/PRs stale after 30/60 days, and
then closes them after an additional week of inactivity.  Anybody who
cares about a particular issue/PR is welcome to help keep it open by
stating their case in a comment.

The stale tag gets cleared by adding a comment to the issue/PR, or by
manually removing the stale tag.

An assignee can be added to a long-term issue/PR to prevent it from
getting marked stale.

The action (which adds/removes stale tags, adds comments, and closes
issues/PRs) runs daily at 10:00 UTC.

Suggested-by: Joe Lawrence <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>

.github/workflows/stale.yml

@@ -0,0 +1,27 @@
+name: close inactive issues
+on:
+  schedule:
+    - cron: "0 10 * * *"
+
+jobs:
+  close-issues:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/stale@v5
+        with:
+          days-before-issue-stale: 30
+          days-before-issue-close: 7
+          stale-issue-label: "stale"
+          stale-issue-message: "This issue has been open for 30 days with no activity and no assignee.  It will be closed in 7 days unless a comment is added."
+          close-issue-message: "This issue was closed because it was inactive for 7 days after being marked stale."
+          days-before-pr-stale: 60
+          days-before-pr-close: 7
+          stale-pr-label: "stale"
+          stale-pr-message: "This PR has been open for 60 days with no activity and no assignee.  It will be closed in 7 days unless a comment is added."
+          close-pr-message: "This PR was closed because it was inactive for 7 days after being marked stale."
+          exempt-all-assignees: true
+          ascending: true
+          repo-token: ${{ secrets.GITHUB_TOKEN }}