mount method
Incorporates another Router
's routes into this one's.
Implementation
SymlinkRoute<T> mount(String path, Router<T> router) {
final route = SymlinkRoute<T>(path, router);
_mounted[route.path] = router;
_routes.add(route);
//route._head = RegExp(route.matcher.pattern.replaceAll(_rgxEnd, ''));
return route;
}