Refactor `Formatter` to `IntlWrapper`

As I needed `Intl.DisplayNames` I've been thinking maybe we should rename the `Formatter` into `IntlWrapper` and wrap all [other APIs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl) as well: - [ ] Collator - [ ] DisplayNames - [ ] DurationFormat - [ ] ListFormat - [ ] PluralRules - [ ] Segmenter What do you think?