add dependabot auto merge workflow

.github/workflows/dependabot-automerge.yaml

@@ -0,0 +1,22 @@
+name: Dependabot auto-merge
+
+on:
+  pull_request_target:
+    branches: [ main ]
+    types: [ opened ]
+
+permissions:
+  pull-requests: write
+  contents: write
+
+jobs:
+  enableAutoMerge:
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.user.login == 'dependabot[bot]'
+    steps:
+      - name: Enable auto-merge for Dependabot PRs
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+