Add 256 color support for fg and bg colors

[vinayak-mehta]

trafficstars

[henryiii]

A way to theme these would be nice, as well (a way to set the default colors - maybe a yaml / toml front matter / stylesheet ?).

By the way, pandoc slides are another popular way to create slideshows from markdown, it might make sense to try to copy to stay as close as reasonable to their syntax?

[vinayak-mehta]

Thanks for the pointer! I'll look into them.