Add Google Translate Pro to g.json

I know there is already a Google Tranlate plugin for github.
But it just redirect user to google website. Useless I guess. 
And the author has abandoned it.

I made a pull request last year, but you didn't accept. The author said he would update his plugin but never did.

So hopfully you can approve this commit.

It works on ST2 & ST3 with proxy support.