Every language should have its own file for the strings (something like en.js, es.js, ru.js), so in the future others can colaborate and merge those changes becomes easier.
Use an existing and supported npm module for this. It's a plus if it has a simpler React integration.
Layout the folder structure and file naming. Provide a working example in one of the pages.
If needed, create actions/reducers to store the current language in the redux store.
Web app should support internationalization.
Considerations:
en.js,es.js,ru.js), so in the future others can colaborate and merge those changes becomes easier.