[Feature Request] Treemaps

[wojciech-graj]

I suggest adding treemap as a type of graph that plotille can draw with a single utility function, akin to scatter and hist.
If this sounds like something that would suit the project, I'd gladly work on this, so feel free to assign the issue to me.

[tammoippen]

Hi there, this sounds like a very nice addition. Please give it a try 😃 .