add auto-merge

.github/workflows/auto-merge.yml

@@ -0,0 +1,21 @@
+name: Steward Auto Merge
+on:
+  pull_request:
+    branches:
+      - main
+permissions:
+  pull-requests: write
+  contents: write
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if:
+      ${{ startsWith(github.head_ref, 'auto/') && github.actor == 'github-actions[bot]' }}
+    env:
+      PR_URL: ${{github.event.pull_request.html_url}}
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Approve PR
+        run: gh pr review "$PR_URL" --approve
+      - name: Enable auto-merge for Steward PRs
+        run: gh pr merge --merge --auto "$PR_URL"