bindStream method
Binds an existing Stream<T> to this Rx<T> to keep the values in sync.
You can bind multiple sources to update the value.
Closing the subscription will happen automatically when the observer
Widget (GetX or Obx) gets unmounted from the Widget tree.
Implementation
void bindStream(Stream<T> stream) {
final listSubscriptions =
_subscriptions[subject] ??= <StreamSubscription>[];
listSubscriptions.add(stream.listen((va) => value = va));
}