docs(operators): clarify that `find` can emit `undefined` (#6538)
docs(operators): clarify that `find` can emit `undefined` (#6538)


ReactiveX/rxjs,martinsik/rxjs,ReactiveX/RxJS,ReactiveX/rxjs,ReactiveX/RxJS,martinsik/rxjs,martinsik/rxjs,ReactiveX/rxjs,martinsik/rxjs,ReactiveX/RxJS,ReactiveX/RxJS,ReactiveX/rxjs