Added tranlsation_belarusian string

[Belarusan]

What is it?

• [ ] Bugfix
• [x] Feature
• [ ] Codebase improvement

Description of the changes in your PR

• Update strings

Acknowledgement

• [x] I read the contribution guidelines.

P. S. „Belarusan“ (without the 'i') is not a mistake or typo. This is how the old Belarusan diaspora writes (or wrote), and it is also how the Belarusan linguist Vincuk Viačorka recommends to write it.