Configuration of mathjax 2 for preview

[melsophos]

I think it could be very useful if users could define themselves Mathjax 2 configuration, in particular the part.

The point is that several important Latex packages (physics, etc.) have been ported to Mathjax but are not available in the preview. For example, the package physics for Mathjax 2 is not loaded since the command \ket{} is not defined (and adding \require{physics}, as recommended in the link in #914, does not enable it).

I have read previous requests for this: #914, #991, #2623. Note that my feature request is different: I am not asking for implementing a specific package or way to load Latex packages (which is not possible in Mathjax 2), but to be able to configure Mathjax 2 (and which Mathjax 2 packages are loaded).

[tamuratak]

Out of the scope of the extension.

MathJax v2 and v3 are drastically different. And, we have to migrate to v3 eventually.

We don't want to put our efforts to configuring MathJax v2.