BREAKING CHANGE: It's now needed to explicitly import the `getClientLocale` method to use
its heuristics when setting the initial locale. This makes the method
and its helpers to be tree-shakeable.
```js
import { init, getClientLocale } from 'svelte-i18n'
init({
initialLocale: getClientLocale({ ... })
})
```
BREAKING CHANGE: Changes completely the API. Now, to format a number, date or time, the
developer must explicitly import the formatter store:
`import { time, date, number } from 'svelte-i18n'`
