Add Belarusian i18n

[MeFoDy]

Based on #60.

Has the same problems as Vadim mentioned there:

Some words needs to be inflected for proper grammar: 1 шаг, 2 шага, 5 шагов (1, 2, 5 steps). There is a lazy way of solving this: шаги: 1, 2, 5 (steps: 1, 2, 5), but requires some changes in templates too. Who knows, maybe there’s something in Intl.PluralRules() that might help.`

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[tomayac]

Thank you very much! I'd usually announce a new language with the flag of the country of origin of the translator, but in this case I made an exception. You still get the hearts 🤍❤️🤍!