Use viewport in an nk_begin

[red-pyramid-games]

There was a discussion in the old repo about drawing the viewport in a nk window, but it seems like it died.
I also saw an image of someone doing this in the show off thread but it seems like their only game engine was in java and didn't appear to use a nuklear binding (could be wrong).

That being said, it seems like it should be possible, just looking for some help to get it done. I'm using the glfw3 backend for my project.

Link to old thread: https://github.com/vurtun/nuklear/issues/552l
Link to show off thread: #251
Here is the image I'm referring to

Thanks for any help!