Add Turkmen translation

[dayanchm]

Summary

Add Turkmen (tk) to the React documentation translations list.

• Language: Turkmen
• Native name: Türkmençe
• Language code: tk

I’d like to help start and maintain the Turkmen translation of the React documentation.

[dayanchm]

Translation experience:
I maintain Turkmen open-source projects and datasets and have experience working with Turkmen-language technical content.

@dayanchm
@agajansahatov

We are both native Turkmen speakers and would like to maintain the Turkmen React documentation translation.