chore: add action to detect and close stale issues

Using this GH action will prevent issues and pull requests from sitting unattended for more than 30 days.

Ref: https://github.com/actions/stale

Author: lance

.github/workflows/stale.yml

@@ -0,0 +1,21 @@
+name: Mark stale issues and pull requests
+
+on:
+  schedule:
+  - cron: "0 0 * * *"
+
+jobs:
+  stale:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/stale@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        stale-issue-message: 'This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days'
+        days-before-stale: 30
+        days-before-close: 5
+        stale-pr-message: 'This pull request is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days'
+        stale-issue-label: 'no-issue-activity'
+        stale-pr-label: 'no-pr-activity'