I am attending GitHub recently, and I have not found another way to offer a translation. Anyway, here's the translation file:
ru_ru.zip

I also suggested adding new settings in another issue, here is their translation into russian:

Изменять фон в указанный период времени: [ Да ]
Время начала: [21:00]
Время окончания: [6:00]

I've added it to version 1.6.2, thanks :)

(not on CurseForge yet because the site broke or something)

Edit: nevermind it should appear here on CurseForge soon: https://www.curseforge.com/minecraft/mc-mods/dark-loading-screen/files/3175263