ci: add dependabot auto approve

Author: piksel

.github/workflows/dependabot-approve.yml

@@ -0,0 +1,12 @@
+name: Auto approve dependabot PRs
+
+on: pull_request_target
+
+jobs:
+  auto-approve:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - uses: hmarr/auto-approve-action@v3