ci(github): new action for auto-merge

* add new GitHub action to merge pull requests from dependabot automatically

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

@@ -0,0 +1,24 @@
+# from https://docs.github.com/en/code-security/supply-chain-security/keeping-your-dependencies-updated-automatically/automating-dependabot-with-github-actions
+name: Dependabot auto-merge
+on: pull_request
+
+permissions:
+  pull-requests: write
+  contents: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v1.1.1
+        with:
+          github-token: "${{ secrets.GH_TOKEN_MERGE }}"
+      - name: Enable auto-merge for Dependabot PRs
+        if: ${{steps.metadata.outputs.update-type == 'version-update:semver-minor'}}
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GH_TOKEN_MERGE}}