Create remove-stale-prs workflow (#1337)

.github/workflows/remove-stale-prs.yml

@@ -0,0 +1,20 @@
+name: 'Close stale issues and PR'
+on:
+  schedule:
+    - cron: '0 0 * * 1-5'
+
+jobs:
+  remove-stale-prs:
+    name: Remove stale PRs
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/[email protected]
+        with:
+          debug-only: true
+          exempt-pr-labels: 'DO_NOT_CLOSE'
+          stale-pr-message: 'This PR is stale because it has been open 7 days with no activity. Remove the `Stale` label or add a comment - otherwise this will be closed in 7 days.'
+          close-pr-message: 'This PR was closed because it has been stale for 7 days with no activity.'
+          days-before-issue-stale: -1
+          days-before-issue-close: -1
+          days-before-pr-stale: 7
+          days-before-pr-close: 7