But I'll bite: What's wrong exactly with using Github's markdown renderer?
This is a plain markdown file, the author could host it on S3 and it'd look like:
https://gist.githubusercontent.com/evadne/c9aeca424d30f024ba...
There are a ton of markdown renderers, author could write one in a few hours for the feature used (#, ##, ###, >, and unordered lists), or even better, paste the thing in one of the many markdown-to-html tools (https://markdowntohtml.com/).
This is not like the author used some proprietary syntax, that only displays on Github.
GitHub has forked Markdown in a way that is incompatible with CommonMark, GitLab, etc. So the author might accidentally buy into that fork which there is no quality control for (just look at the lack of care put into their attempt at admonitions).
You can share it elsewhere if like