CI: automatically approve & merge Dependabot PRs (#1720)

Co-authored-by: Davor Runje <[email protected]>

.github/workflows/dependabot_automerge.yaml

@@ -0,0 +1,27 @@
+name: Dependabot automerge
+
+on:
+  pull_request_target:
+
+jobs:
+  automerge:
+    name: Enable pull request automerge
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.user.login == 'dependabot[bot]'
+
+    steps:
+      - uses: alexwilson/[email protected]
+        with:
+          github-token: ${{ secrets.AUTOMERGE_TOKEN }}
+          merge-method: REBASE
+
+  autoapprove:
+    name: Automatically approve pull request
+    needs: [automerge]
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.user.login == 'dependabot[bot]'
+
+    steps:
+      - uses: hmarr/auto-approve-action@v4
+        with:
+          github-token: ${{ secrets.AUTOMERGE_TOKEN }}