Enable translations for en-* languages

[amaury1093]

We have translations for Spanish #79 and French Portuguese #89. They should not be enabled before we actually make sure they don't break the design (e.g. words too long).

However, for en-* languages, we could already support them, as there's little risk of breaking the design. So the idea would be to have en-GB.json, en-US.json and even other en-*.json language files, and replace

https://github.com/amaurymartiny/shoot-i-smoke/blob/e1305b684a086c6b7c1a9c1c70a7bca65bc12dd6/App/localization/index.ts#L32-L34

with loading the actual correct language file corresponding to the user's phone's locale.