docs: align jwt-auth README with public API

[gustavomarques00]

Summary

Reopens the jwt-auth README correction on top of the current main branch after PR #24 was merged first.

Changes

• Adds role-based authorization to the package description and recruiter summary.
• Adds middleware.protectWithRoles(roles) to the public API reference table.
• Adds a role-based route usage example.
• Removes the outdated note saying protectWithRoles was not part of the public API.
• Updates the roadmap to mark role middleware as exported.

Validation

Documentation-only change.