source highlighting

[jaredh159]

https://docs.asciidoctor.org/asciidoc/latest/verbatim/source-highlighter/

going to need to think about this one. looks like some backends of asciidoctor pull in dependencies like rouge (ruby) or pygments (python) and do the highlighting as part of the conversion process.

not sure if/how to match this, maybe there's a rust library that can do this, or some sort of pluggable way to interface with other libs.