Require reviewer checklist (#13601)

* Create require-checklist.yml

* Add debug

* Fix github event

* Add repofullname and prnum

* Fix repo path

* Avoid empty vars

* Simplify

* Fixes

* Cleanup

* trigger on pr to master only

* mplesa review

* trigger on 1.* branch

* Switch to `gh pr`. Sed for printing.

.github/workflows/require-checklist.yml

@@ -0,0 +1,20 @@
+name: Require Reviewer Checklist
+
+on:
+  pull_request:
+    types: [opened, reopened, edited, synchronize]
+    branches: [master, 1.*]
+
+jobs:
+  require-reviewer-checklist:
+    runs-on: ubuntu-latest
+    steps:
+      - env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          REPO_NAME: ${{ github.event.repository.full_name }}
+          PR_NUMBER: ${{ github.event.number }}
+        run: |
+          if gh pr view "$PR_NUMBER" -R "$REPO_NAME" --json body --jq '.body' | sed -n '/## Reviewer Checklist/,/## After-merge Checklist/p' | grep '\[ \]'; then
+              echo "Found unchecked reviewer items. Failing..."
+              exit 1
+          fi