Add simplified chinese option for Google Translate

[dcunhas]

I noticed that, when translating from Chinese using Google Translate that this extension defaults to using Google Translate's traditional Chinese translation. Notably, they offer both traditional and simplified Chinese translations. I would like the option to choose between these translators.

[vitonsky]

Linguist currently does not use second part of languages defenitions in codes like zh-TW (here this is TW).
So when Linguist see code zh-TW, it uses zh language.

Share your thoughts how your feature may be implemented.

It would be too weird a bit to introduce option to set preferred language variant, because actually the world have really many language variants, and we can't control when it possible to use some variant in translators.