math (katex) support

[aarmn]

Is your feature request related to a problem?

after adding support for language syntax highlight, it just make sense to support katex math as well

Describe the solution you'd like

katex math syntax support with $$math$$ or $math$
or
```latex
```
or
```math
```
or
```katex
```
and rendering math in the msg box

Describe alternatives you've considered

sending image of the math formula

Additional context

No response

[ilya-fedin]

Syntax highlighting rules are outsourced to the prism.js library, it's not a part of tdesktop itself.