Import all locales

Is it possible to import all locales?
instead of doing them all manually like this

```
import 'dayjs/locale/en';
import 'dayjs/locale/de';
....
```

import all of them?

Start by tracing how the locale modules under dayjs/locale, such as en and de, are imported and packaged. The issue names no source file or test, so first identify the relevant entry point and existing locale-loading tests. Done means users have a documented way to import all locales without listing each one manually.

Written by the indexing model from the issue text.