[PRI][WIP] update the JSON format for the translation file en.json

:koala::+1:

This PR intends to update the JSON format of the en translation file.

<h2>TASKS</h2>
@svizzari , @maximeprades, and @tmcinerney  can you please review this format? I am happy to further refine it if there is any error :)

/cc @zendesk/quokka