fix: custom paths pages config should use route name as key

[BobbieGoede]

🔗 Linked issue

• Nested route path was not translated #3185

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Resolves #3185

It appears the documentation is incorrect and has likely been so since v9, at the moment custom paths configuration using the pages property only supports using route paths (without leading /) as keys, this is especially problematic since the generated types with experimental.typedPages will give type completion for route names as keys...

This PR resolves this by supporting both paths and names as keys, and I am planning to deprecate the path keys in the next major version. I'm not 100% sure if this has potential to collide with existing path configurations, but I haven't found scenarios in which that would be possible, if there are we may need to make this change configurable (opt-in), but supporting both would mean the existing documentation would be correct again.

📝 Checklist

• I have linked an issue or discussion.
• I have added tests (if possible).
• I have updated the documentation accordingly.