Add check for non-public feed URLs

Author: mbg

.github/workflows/pr-checks.yml

@@ -95,6 +95,14 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
+      - name: Check for incorrect addresses in package-lock.json
+        run: |
+          if git grep -nE '(pkgs\.visualstudio\.com|pkgs\.dev\.azure\.com|packagefeedproxy\.microsoft\.io)' -- \
+              'package-lock.json'; then
+            echo "::error::package-lock.json contains internal package feed URLs. Replace them with public registry URLs."
+            exit 1
+          fi
+
       - name: Set up Node.js
         uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with: