|As a start, I built a prototype.|
I wrote a utility script of sorts, that takes the manpages from the source code, and the troff into Markdown.
I've added a preview of what zshcontrib(1) looks like when it is converted to Markdown, and I've also posted a GitHub gist of the manpage when the script converts it back from Markdown into troff. Key takeaway: this utility script can convert the manpages bidirectionally between troff and Markdown.
This utility script is just a wrapper around Pandoc, so it's nothing fancy, there's not much that would need to be maintained, and performing the conversions is designed to be straightforward enough as for anyone working on the project to be able to do so themselves.
Anyway, this is still a work in progress, so if you have any thoughts, or see any ways this tool could be improved, or a better way to apply the technology, I am all ears.
P.S.: Shout out to Oliver Kiddle and Daniel Shahaf, who took the time to welcome me into the project and give me important guidance/direction as I went about making my first contribution to the Zsh project.