The language system uses the vanilla mincraft names to identify the language file,
so if you are playing on english from UK, you need to copy the en_US file and rename it
to en_UK, same with all the languages.
If you are interested in editting, or adding new languages, here are some specifications:
For items: all the items(name and description), starts with "item."+name of item.
The item name will never have any number at the end, the "item.nameofitem0","item.nameofitem1"
its used for the item description, you can remove them or add more(allways in orded and starting
from 0, if the 0 its missing no description will appear)