Katex functions not supported

[rahulpathakgit]

Boostnote - 11.12
OS: Ubuntu 16.04

There are multiple Katex functions which are not supported by Boostnote.. For instance

$$\real$$, $$\reals$$ nothing works.
Error: KaTeX parse error: Expected 'EOF', got '\reals' at position 1: \̲r̲e̲a̲l̲s̲

[Flexo013]

Can be closed due to #2998.