Add support of typst formula blocks

[Roseleaves]

typst is a brand new formatting system as an advantage of latex, which abandoned most of the backslashes, and still keep it precise to compile.

when use $...$ and normal $$...$$, still use mathjax or katex; However, when use such forms below, where a total line is a word typst after two dollars, then use typst to compile.

$$typst
pi = n R T / V
$$