feat: add auto-merge for dependabot PRs

Author: dacrab

.github/workflows/auto-merge-dependabot.yml

@@ -0,0 +1,20 @@
+name: Auto-merge dependabot PRs
+
+on:
+  pull_request_target:
+    types: [opened, synchronize, reopened, ready_for_review]
+  check_suite:
+    types: [completed]
+
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    
+    steps:
+      - name: Enable auto-merge for dependabot PRs
+        run: |
+          gh pr merge --auto --squash --delete-branch "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}