Add dependabot automerge

.github/workflows/dependabot-automation.yaml

@@ -0,0 +1,31 @@
+---
+name: Dependabot automation
+
+on:  # yamllint disable-line rule:truthy
+  pull_request:
+    types:
+      - opened
+      - synchronize
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot:
+    env:
+      PR_URL: ${{github.event.pull_request.html_url}}
+      GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - name: Fetch Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v2
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Approve the PR
+        run: gh pr review --approve "${PR_URL}"
+      - name: Enable auto-merge for PRs
+        run: gh pr merge --auto --squash --delete-branch "${PR_URL}"
+...