Add docs for route-specific CORS

[WendellAdriel]

This PR documents the new route-specific CORS support so developers can configure cross-origin policies where routes are defined instead of relying only on global configuration.

Framework PR: laravel/framework#59305

Usage

The docs now cover route-level ->cors([...]) usage, route group inheritance, and the #[Cors] attribute on controller classes and methods.

Approach

• Extend the routing documentation's CORS section with the new per-route configuration workflow.
• Show the supported options and explain precedence between route, group, class, and method definitions.
• Note that route-specific CORS metadata continues to work with route caching.