Promise.all 
by Anthony Fu @antfu
给函数`PromiseAll`指定类型，它接受元素为 Promise 或者类似 Promise 的对象的数组，返回值应为`Promise`，其中`T`是这些 Promise 的结果组成的数组。
```ts
const promise1 = Promise.resolve(3);
const promise2 = 42;
const promise3 = new Promise((resolve, reject) => {
setTimeout(resolve, 100, 'foo');
});
// 应推导出 `Promise<[number, 42, string]>`
const p = PromiseAll([promise1, promise2, promise3] as const)
```
