Language system

[Mondei1]

Describe the solution you'd like
We should add a language system based on JSON to handle multiple languages. So it looks like that:

{
    "welcome": "Welcome {0}, how is your day going?"
}

and stored in src/assets/locale/en.json.

There should be a language registry in src/assets/locale/config.json contains:

{
    "languages": [
        {
            "name": "de", # TypeOS will search in src/assets/locale/de.json
            "fullName": "German", # Full english name of language
            "nativeName": "Deutsch" # Native language name
        }
    ]
}