Add npm package to node installation

Adds npm alongside nodejs for better package management support in GitHub Actions runners.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jackluo923

build/config.json

@@ -81,7 +81,8 @@
       "category": "node",
       "source": "apt",
       "packages": [
-        "nodejs"
+        "nodejs",
+        "npm"
       ]
     },
     {