Add a dependency review PR check

Copies https://github.com/alphagov/notifications-api/pull/4769/files

Author: quis

.github/workflows/dependency-review.yaml

@@ -0,0 +1,14 @@
+name: 'Dependency Review'
+on: [pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  dependency-review:
+    runs-on: ubuntu-latest
+    steps:
+     - name: 'Checkout Repository'
+       uses: actions/checkout@v5
+     - name: Dependency Review
+       uses: actions/dependency-review-action@v4