zip<B, F> method
Combines this fiber with another fiber, returning when both complete
Implementation
Future<(Exit<A, E>, Exit<B, F>)> zip<B, F>(Fiber<B, F> other) async {
final results = await Future.wait([_future, other._future]);
return (results[0] as Exit<A, E>, results[1] as Exit<B, F>);
}