Note that I changed the language names to lookup from {lang}-{region} instead of
just {lang}, because Genshin Impact supports both zh-cn and zh-tw locales.
zh-tw's tranlsation is different zh-cn.
Standard German language code is `de` but game API requires it to be `de-de`.
With this change formatted locales always will have
region so always will fit game requirements
Improved `i18n` mod to list supported languages and some other stuff
As well was added `get_default_lang` function
which will return language key based on current system language.
This function is called at the first launcher start
to update default `launcher.language` config property, so user will immediately
have proper language in initial setup window
