Promise finally

[Raul-Sebastian Mihăilă]

I find it weird that

```js
Promise.resolve().finally(() => {}).then(() => { console.log(1); });
Promise.resolve().then(() => {}).then(() => { console.log(2); });
```

prints 2 and then 1. It would have been possible to spec it in such a way
that it would have printed 1 and 2.

On the other hand

```js
Promise.resolve().finally().then(() => { console.log(1); });
Promise.resolve().then().then(() => { console.log(2); });
```

prints 1 and then 2.
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