ci: update workflows

.github/dependabot.yml

@@ -3,13 +3,13 @@ updates:
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "weekly"
+      interval: "monthly"
     labels:
       - "dependencies"
 
   - package-ecosystem: "npm"
     directory: "/"
     schedule:
-      interval: "weekly"
+      interval: "monthly"
-    allow:
+    labels:
-      - dependency-name: "@actions/*"
+      - "dependencies"

.github/workflows/automerge-dependabot.yml

@@ -0,0 +1,13 @@
+name: Auto-merge Dependabot
+on: pull_request
+
+jobs:
+  automerge:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - uses: peter-evans/enable-pull-request-automerge@v2
+        with:
+          token: ${{ secrets.DEPENDABOT_AUTOMERGE }}
+          pull-request-number: ${{ github.event.pull_request.number }}
+          merge-method: squash