TeXify is a GitHub app that renders TeX expressions in README files.
However, I haven't found a way to make it work nicely with a website
hosted on GitHub Pages. Relative links are also handled a bit
differently with GitHub Pages, which sometimes causes issues. For
those reasons, I am now dropping support of the REPL as a website in
favor of simple GitHub README files directly accessible on GitHub.
Because mathematics are key to our understanding, I am favoring
TeXify over the looks of a better design. If a solution comes up,
I will gladly re-add support for GitHub Pages.