Introduce auto-merge idea for dependabot

Ref: https://docs.github.com/en/code-security/dependabot/working-with-dependabot/automating-dependabot-with-github-actions#enable-auto-merge-on-a-pull-request

Introduce auto-merge idea for dependabot.

.github/workflows/auto-merge.yml

@@ -0,0 +1,28 @@
+---
+name: Dependabot auto-merge
+
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+    - name: Dependabot metadata
+      id: metadata
+      uses: dependabot/[email protected]
+      with:
+        github-token: "${{ secrets.GITHUB_TOKEN }}"
+
+    - name: Enable auto-merge for Dependabot PRs
+      if: ${{ steps.metadata.outputs.update-type == 'version-update:semver-patch' }}
+      env:
+        PR_URL: ${{github.event.pull_request.html_url}}
+        GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+      run: |
+        gh pr review --approve "$PR_URL"
+        gh pr merge --auto --merge "$PR_URL"