Promise with a time limit

Implement promiseTimeout(promise, ms). It returns a new promise. If promise settles within ms milliseconds, the new promise settles the same way. Settles means resolves or rejects.

• If promise resolves or rejects first, pass on its value or reason.
• If ms ms pass first, reject with an Error whose message is exactly Timed out after <ms> ms. For example: Timed out after 100 ms. A late result from promise is then ignored.
• When promise settles in time, clear the timer so nothing is left pending.