Function: onOrientation() 
onOrientation():
Stream<"portrait"|"landscape">
Defined in: streams/onOrientation.ts:21
Creates a stream that emits the current screen orientation, either "portrait" or "landscape", whenever it changes.
Automatically unsubscribes when unsubscribed.
Returns 
Stream<"portrait" | "landscape">
A stream that emits a string indicating the screen's orientation.