Add workflow to enable auto-merge for dependabot (#95)

Author: lucacome

.github/workflows/dependabot-auto-merge.yml

@@ -0,0 +1,18 @@
+name: Dependabot auto-merge
+on: pull_request_target
+permissions:
+  pull-requests: write
+  contents: write
+jobs:
+  dependabot:
+    runs-on: ubuntu-20.04
+    if: ${{ github.event.pull_request.user.login == 'dependabot[bot]' }}
+    steps:
+      - name: Dependabot metadata
+        id: dependabot-metadata
+        uses: dependabot/[email protected]
+      - name: Enable auto-merge for Dependabot PRs
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{ secrets.NGINX_PAT }}