[project] Parsing LaTeX as a source (`mdast`)

[mmcky]

The myst-spec and mystjs projects have been focused on using mdast as the abstract syntax tree representation.

One project (as identified by @rowanc1) is to explore the possibility of having LaTeX as a source using:

https://github.com/siefkenj/latex-parser

[mmcky]

cc: @AakashGfude