Let a subject notify a list of subscribed observers whenever its state changes, without the subject knowing anything concrete about who's listening.
Implement `Subject.subscribe(name)`/`notify(value)`: every subscribed observer's update(value) should log { observer: name, value } when notified.
solve(names, values) subscribes every name, then calls notify for every value, and returns the full log.
solve(['a', 'b'], [1]) → [{ observer: 'a', value: 1 }, { observer: 'b', value: 1 }]
Sample tests