[Wishlist] spell checking : add multi language support

[Nizar Kerkeni]

I'm using gwibber in different languages -as many others users i suppose- and it would be great if we can get the possibility to do spell checking in these different languages.
As jens persson said on https://bugs.edge.launchpad.net/gwibber/+bug/252857/comments/1 it's possible to to make the language configurable, ie. when right clicking on the input field let the user select what language to use.
Note : the bug #252857 is marked as fixed but i'm using gwibber 1.2.0 and i haven't this possibility.