Add workflow to mark stale issues and PRs (ava-labs#1443)

.github/workflows/stale.yml

@@ -0,0 +1,28 @@
+name: Mark stale issues and pull requests
+on:
+  schedule:
+    - cron: '0 0 * * 0' # Run every day at midnight UTC on Sunday
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v8
+        with:
+          # Overall configuration
+          operations-per-run: 100
+
+          # PR configuration
+          days-before-pr-stale: 30
+          stale-pr-message: 'This PR has become stale because it has been open for 30 days with no activity. Adding the `lifecycle/frozen` label will cause this PR to ignore lifecycle events.'
+          days-before-pr-close: -1
+          stale-pr-label: lifecycle/stale
+          exempt-pr-labels: lifecycle/frozen
+          close-pr-label: lifecycle/rotten
+
+          # Issue configuration
+          days-before-issue-stale: 60
+          stale-issue-message: 'This issue has become stale because it has been open 60 days with no activity. Adding the `lifecycle/frozen` label will cause this issue to ignore lifecycle events.'
+          days-before-issue-close: -1
+          stale-issue-label: lifecycle/stale
+          exempt-issue-labels: lifecycle/frozen
+          close-issue-label: lifecycle/rotten