Internationalization of terria

[zoran995]

Starting this so we can track work on internationalization of app, hope it is ok

[zoran995]

@rowanwins and @soyarsauce How we should proceed with data in defaults.jsx? I am not sure is it possible to keep it as it is with i18next

[soyarsauce]

We should continue the rest of the internationalisation efforts in the work done through #3787, and stop using defaults.jsx for i18n - however it could still be useful for defining other ways to extend terria (see https://github.com/TerriaJS/de-australia-map/pull/29/files#diff-e7c237f2b6a10131a063f7b5740c39aaR5)

[zoran995]

I will post some questions:

• language switch:

  • Where should we put a button for users to switch languages of the map in the TerriaMap or TerriaJS? The user should have an option to define languages that he want to enable. The switcher should not be visible by default if there is only one language in the Language folder.
  • From the design perspective dropdown or something else, and where to position it?
  • Should we show the country flag next to language name (if yes then user should also have option to choose that)?

• should we split translation.json file to multiple parts to separate ReactViews translation from the rest (core, models and map which are biger groups in the translation.json)