onRoutesChanged
Invoked whenever a list of routes changes and immediately when registered (see MapboxNavigation.registerRoutesObserver) if non-empty routes are present.
The route at index 0, if exist, will be treated as the primary route for 'Active Guidance'.
A list of routes can be modified internally and externally at any time with MapboxNavigation.setRoutes, or during automatic reroutes, faster route and route refresh operations.