Add auto-merge workflow for trusted contributors (#121)

Author: gaborbernat

.github/workflows/auto-merge.yaml

@@ -0,0 +1,20 @@
+name: Auto-merge
+on:
+  pull_request_target:
+    types: [opened, synchronize, reopened]
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  auto-merge:
+    name: 🤝 Auto-merge
+    runs-on: ubuntu-latest
+    if: github.actor == 'gaborbernat' || github.actor == 'dependabot[bot]' || github.actor == 'pre-commit-ci[bot]' || github.actor == 'github-actions[bot]'
+    steps:
+      - name: 🔀 Enable auto-merge
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}