Use dependabot via GitHub actions

.github/dependabot.yml

@@ -0,0 +1,22 @@
+version: 2
+
+updates:
+  - package-ecosystem: bundler
+    directory: "/"
+    schedule:
+      interval: daily
+      time: "09:00"
+      timezone: UTC
+    labels:
+      - dependencies
+      - ruby
+
+  - package-ecosystem: npm
+    directory: "/"
+    schedule:
+      interval: daily
+      time: "09:00"
+      timezone: UTC
+    labels:
+      - dependencies
+      - javascript

.github/workflows/dependabot.yml

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+name: Dependabot Automerge Check
+on:
+  - pull_request
+
+jobs:
+  worker:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Automerge dependabot dependencies
+        uses: actions/github-script@v3
+        if: github.actor == 'dependabot[bot]'
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            github.pullRequests.createReview({
+              owner: context.payload.repository.owner.login,
+              repo: context.payload.repository.name,
+              pull_number: context.payload.pull_request.number,
+              event: 'APPROVE'
+            })
+            github.pullRequests.merge({
+              owner: context.payload.repository.owner.login,
+              repo: context.payload.repository.name,
+              pull_number: context.payload.pull_request.number
+            })