docs: add notifier breaking changes (#6299)
docs: add notifier breaking changes (#6299)

Closes #6298
martinsik/rxjs,martinsik/rxjs,martinsik/rxjs,ReactiveX/rxjs,ReactiveX/RxJS,benlesh/RxJS,ReactiveX/rxjs,ReactiveX/RxJS,benlesh/RxJS,ReactiveX/rxjs,benlesh/RxJS,ReactiveX/RxJS,ReactiveX/rxjs,ReactiveX/RxJS,benlesh/RxJS,martinsik/rxjs