Default plural formula should probably be the one for English

[cbosdo]

In most programs the default language is English. Should this be reflected in the formula of the nilTranslator instead of the no-plural one?
If that is not desirable, because changing a default may have an impact on other programs, then adding an API to allow changing it would be nice.

[cbosdo]

Here is a workaround I implemented using a default FileSystem implementation that returns an empty json: https://github.com/uyuni-project/uyuni-tools/blob/main/shared/l10n/utils/defaultfs.go