[BUG] URL should be included on package level nodes for docs generation

[xelaint]

🐛 Bug report

Current Behavior

Using main package URLs for the packages overview page. Noticed that packages with child markdown files have a url of /undefined

Expected Behavior

Include the URL on package level nodes.

Minimal reproduction of the problem with instructions

1. navigate to next.daff.io/guides or next.daff.io/packages (depending on if certain PRs have been merged)
2. Click on the @daffodil/cart card
3. Should redirect to /404 because the route is /undefined

[damienwebdev]

This appears corrected. On https://next.daff.io/docs/packages

works as expected and navigates you to https://next.daff.io/docs/packages/cart