Added a passthrough for scoped middleware in actix-web

[nico-incubiq]

This PR adds the ability to register middlewares at a specific Scope using a fluent API, similar to the one of actix-web's Scope struct.

Before:

utoipa_actix_web::scope(
    actix_web::web::scope("/admin")
        .wrap(Authenticated::new("/admin"))
    )
    .service(admin_dashboard)

After:

utoipa_actix_web::scope("/admin")
    .wrap(Authenticated::new("/admin"))
    .service(admin_dashboard)

[juhaku]

Nice, thanks 👍 I'll make a release of this soon.

[nico-incubiq]

Thanks :) brilliant project btw!