Add Cyrillic letters

[spertulo97]

I see that the Configurator now has a Russian translation, but it still can't configure Cyrillic layouts.
Without them, the program is useless for many users.
Please add Cyrillic letter support to the program.

[leviport]

Language configuration is out-of-scope for the Keyboard Configurator. Languages should be set in your OS, not in the keyboard's firmware. Keyboard firmware is only capable of being mapped to keycodes of which there aren't enough to be used for internationalization.