i18n is already working at one exact point. Switching it on all over the app is necessary.
Not hard, but need to be done cleanly.
Downstream
This will allow us later to :
- T375653 add projects i18n/en.json to translatewiki
- add first translation to translatewiki (i18n/fr.json) and call for more
- add functioning select language button
- add url parameter ?language=fr for language selection to spread