Add note about named parameters in route

[fadrian06]

Ref: Named Parameters Are Actually In Order... · Issue #584 · flightphp/core
flightphp/core#584

Although Flight supports named parameters in the handlers, that does not mean that the order is not taken into account because it is taken into account.

It would be more helpful to be able to get a fragment of the url as a handler parameter instead of having to get it out of the request or the Route object.