Prism themes

[pwwang]

I have made the prism themes for plotnine:

https://github.com/pwwang/plotnine-prism

which turns:

to:

So should I make a PR or just keep it an independent package?

[has2k1]

This is good. For now, it should remain independent it isn't just a simple theme. I think we need a good container for such type of comprehensive theming.