docs(routing): add nested example

[geromegrignon]

🔗 Linked issue

2415

❓ Type of change

• [x] 📖 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

Nesting routes with file based routing and using index files might be missing from an user's perspective. Id adds a more complete example of a structure.

📝 Checklist

• [x] I have linked an issue or discussion.
• [x] I have updated the documentation accordingly.

[geromegrignon]

Partially unrelated, i'm unsure about this note:

Does it mean the folder structure for standalone nitro is /api and /routes, while prefixed by serverfor Nuxt apps? Because by creating a standalone nitro app nowadays, there is a root server folder too.

[atinux]

Does it mean the folder structure for standalone nitro is /api and /routes, while prefixed by serverfor Nuxt apps? Because by creating a standalone nitro app nowadays, there is a root server folder too.

Nice catch, I think we can now remove this alert in the docs.