Add automerge workflow for dependabot PRs

Author: jeswr

.github/workflows/automerge.yml

@@ -0,0 +1,20 @@
+name: Enable automerge on dependabot PRs
+
+on:
+  pull_request_target:
+
+jobs:
+  automerge:
+    name: Enable automerge on dependabot PRs
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+      repository-projects: write
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - uses: actions/checkout@v6
+      - run: gh pr merge ${{ github.event.pull_request.html_url }} --auto --squash
+      - run: gh pr review ${{ github.event.pull_request.html_url }} --approve
+    env:
+      GH_TOKEN: ${{ github.token }}