insert method
Inserts the corresponding page to given route
to the _pages
stack
if onFailure
callback is provided, navigation errors will be passed to it
otherwise they'll be thrown
Implementation
Future<void> insert(PageRouteInfo route, {int index = 0, OnNavigationFailure? onFailure}) {
return _findStackScope(route)._push(route, onFailure: onFailure, insertAt: index);
}