chore: add dependabot auto-merge workflow

Author: jtgsystems

.github/workflows/dependabot-automerge.yml

@@ -0,0 +1,21 @@
+name: Dependabot auto-merge
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize, ready_for_review]
+permissions:
+  contents: write
+  pull-requests: write
+jobs:
+  dependabot:
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: dependabot/fetch-metadata@v2
+        id: metadata
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Enable auto-merge
+        uses: peter-evans/enable-pull-request-automerge@v3
+        with:
+          token: "${{ secrets.GITHUB_TOKEN }}"
+          merge-method: squash