Implement optional route parameters

[wwwtony5488]

Clear and concise description of the problem

The router's pages should support a construction as follows

pages/
 -[[foo]]/
 --bar
 ---index.vue

Suggested solution

It's already implement at Nuxt 3, only need to achieve the same things

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.