Jupyter-book: MathJax \begin{align} rendered as a single line equation

[bsamadi]

Describe the bug
I have a \begin{align} environment in my markdown file to create multiline equations. However, the equations are rendered in a single line. I have used the same source code in a Jupyter Notebook and it works as expected:
https://github.com/bsamadi/cvxguide/blob/master/cvxguide.ipynb

By the way, GitHub rendering has the same issue. I have used the same source in a post made by Hugo and rendered by MathJax 3. It works:
http://www.mechatronics3d.com/post/2014-convex-optimization/

Also, Jupyter can render the same LaTeX problem properly. The issue might be fixed if MathJax 3 is used. My Hugo website uses MathJax 3 and the formula is rendered properly on the MathJax website (online demo).

To Reproduce
Steps to reproduce the behavior, see this page:
https://bsamadi.github.io/cvxguide/ConvexOptimization.html

The source code is:
https://raw.githubusercontent.com/bsamadi/cvxguide/master/cvxguidebook/ConvexOptimization.md

Expected behavior
The result of the \begin{align}\end{align} environment is multiline equations.

[phaustin]

See https://github.com/executablebooks/jupyter-book/issues/604#issuecomment-631176620

[phaustin]

workaround for now -- enclose the environment in $$ delimiters

[chrisjsewell]

Can you check this in v0.8 and see if you get the same issue, see https://jupyterbook.org/content/math.html

As it says there, you now need to use in config:

parse:
  myst_extended_syntax: true