Auto merge dependabot PRs (#755)

This pr:
1. checks if the user == dependabot[bot]
2. if all CI passes, auto approve and merge the PR

Co-authored-by: bee <[email protected]>

Author: bee-san

.github/workflows/dependabot.yml

@@ -0,0 +1,19 @@
+name: Dependabot Auto-Merge
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+      - name: Enable auto-merge for Dependabot PRs
+        run: |
+          gh pr review --approve "$PR_URL"
+          gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}