I18next provides an easy way to translate a website on clientside:
* fetch resources from server
* fetch each resource file individually (static) or all once via dynamicroute
* apply translation to html tags with the _data-i18n_ attribute
* post missing key-value pairs to server (for easy development, just
translate the new keys)
* search for key en-us first, then in en, then in fallback language (or
de-de, de, fallback).