Here's a quick hack I wrote to fetch the reference doc for nginx lua module and convert it to a dash docset. Which I view using our beloved helm-dash.
Quick, and kinda easy. It's totally hackish in the way that I'm parsing HTML with regexps. Not even recursive regexps.....
But the thing is that this html is generated by markdown, and as it's fetching for a very concrete type of lines, they are all formatted the same way.
Another option (less hackish but for this concrete case, equally fragile) is using xmlstarlet. The code is also in the import.sh file (for reference).
So here's the kidd/HttpLuaModule.docset repo.