Document using existing MathJaX (disable?)

[kno10]

Describe the bug

We can set, e.g.,

"mathjaxUrl" = false

to disable mathjax. Yet, the documentation is unclear on the consequences of this: will this disable mathjax completely?

I already use MathJax4, and I already have it configured, hence I do not want thebe to load another version/copy, but simply use the existing mathjax.

This section indicates that thebe relies on the mathjaxUrl to be set:

https://github.com/executablebooks/thebe/blob/cce89f9051b750145081e78ed7cf8deff24ae14e/packages/core/src/rendermime.ts#L29-L56

But on the other hand, this probably only adds "mathjax cell support", interesting for editable math? Furthermore, mathjax2 extension appears to be legacy to me, as jupyter updated to mathjax3 already? jupyterlab/jupyterlab#13877

Reproduce the bug

n/a

List your environment

n/a