Whether to perform the hero transition if the PageRoute transition was triggered by a user gesture, such as a back swipe on iOS.
If Heroes with the same tag on both the from and the to routes have transitionOnUserGestures set to true, a back swipe gesture will trigger the same hero animation as a programmatically triggered push or pop.
The route being popped to or the bottom route must also have PageRoute.maintainState set to true for a gesture triggered hero transition to work.
Defaults to false and cannot be null.
final bool transitionOnUserGestures