Syntax highlighting with Markdown code blocks interacts badly with Mathjax

[arradha]

Any text between $ characters within markdown seems to be rendered in tex math mode using MathJax. However, within code blocks with language specified (e.g., enclosed by ```python and ```), this is almost always the wrong choice. It interacts badly with any syntax highlighting.

See below, where the text '<newline> d = '^[0-9] has the wrong colour and the second = is rendered in the wrong typeface. On the other hand, MathJax is not fully enabled either ``` $\frac{1}{2} $ ``` is rendered as is, and not converted to the math rendering.

[arradha]

A patch is available for this issue is available in #4041.