Promise.race Polyfill

Implement promiseRace(promises), a polyfill for Promise.race.

It takes an iterable of values or promises and returns a promise that settles the same way as the first input to settle: it resolves with that value or rejects with that reason. Plain non-promise values count as already settled. If several are already settled, the earliest in input order wins. An empty input gives a promise that stays pending forever.

Do not call Promise.race.