Incorporate JavaScript Library for LaTeX rendering

[drn05r]

/cgi/latex2png has had to be removed as it was a security vulnerability. It has always been quite a heavyweight approach to providing LaTeX rendering as it requires latex and dvips binary to be installed and additional configuration. A JavaScript library for LaTeX rendering (such as MathJax or KaTeX) would be preferable.

jquery has recently been added as an available 3.4 ingredient within the codebase. A similar mathjax ingredient may be a useful addition, which can then be enabled by repositories that need LaTeX rendering support.