Exercises editor does not allow raw KaTeX

[rtibbles]

Users attempting to write mathematical and scientific symbols have issues as the editor appears to remove extra \ from their input that prevents it being properly rendered.

Attempt to input:

$\\text {Li}_2 \\text SO_4$

And one of the escaping \ will be removed, causing it to be rendered literally in Kolibri.

In addition, while it is possible to make them correctly render in Studio - correctly rendering in Studio is not an accurate indication of them rendering properly in Kolibri.

https://community.learningequality.org/t/issues-with-latex-subscripts/2424/3