Adding localization support in the frontend

[nerlichman]

Description

Do you think that this is something worth having on the starter kit?

If you think so, let me know and I can open the pull request!

In an app we are building, we needed to localize a few pages. In order to do that we made use of i18next and "react-i18next.

Implementation

I decided for a direct approach, initializing i18next on the frontend, using it's own translation files.

Brief description of changes:

• Defined translation files on app/frontend/lib/translations/[LANG].ts
• Initialize i18next on app/frontend/lib/i18next.ts
• Include it on the inertia.tsx entrypoint.
• Pass locale with inertia_shared on InertiaController.
• Add useLocale to react to locale changes.
• Add around_action :switch_locale on ApplicationController to let Rails manage the locale.

Usage

import { useTranslation } from "react-i18next"

export default function Dashboard() {
  const { t } = useTranslation()
  
  return ( <p>{t("dashboard.title")}</p>)
}

[skryukov]

Thanks for the issue, @nerlichman!

There's also https://github.com/fnando/i18n-js, and I can see people preferring to use a single source for all their translations, so I don't know if I want to push someone in one direction or another without a clear advantage.

[nerlichman]

I didn't know about this gem! I initially thought about a single source too, I will have to check it!

From what I understood about the gem, it could work in tandem this suggestion. The gem could generate the json translation files, instead of having to write it manually. But the frontend code would be the same, reading from a json file and setting i18next.