Use goldmark-mathjax extension

[peaceiris]

The inline is ok but the multiline failed.

vim content/post/2020-04-02_mathjax/index.md

$ \begin{vmatrix}a & b \\\\ c & d \end{vmatrix}$

$$
\begin{vmatrix}a & b\\
c & d
\end{vmatrix}
$$