Enable Dependabot auto-merge on successful validation (#28)

* ci: auto-merge dependabot updates

* ci: use official dependabot auto-merge workflow

Author: julienld

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

@@ -0,0 +1,26 @@
+name: Dependabot auto-merge
+
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot:
+    if: github.actor == 'dependabot[bot]'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fetch Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v2
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+
+      - name: Enable auto-merge for Dependabot PRs
+        if: ${{ steps.metadata.outputs.update-type == 'security-update' || contains(fromJson('["version-update:semver-minor","version-update:semver-patch"]'), steps.metadata.outputs.update-type) }}
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{ github.event.pull_request.html_url }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}