feat: allow passing a custom navigator key to routerConfig

[RyanHolanda]

I needed to show a global dialog from a place where the context was no longer available, but the current Routefly version didn’t allow me to pass a custom navigator key to get a global context.

Now, I’ve made it possible to pass a custom navigator key to routerConfig, so anyone who needs a global context or direct access to the navigator key can use it