Change MathJax fonts from STIX-Web to TeX

[mgeier]

Currently, the fonts used by MathJax don't look great, switching to TeX font makes it look much better.

Also, nbviewer seems to be using TeX, so this way both would be consistent.

See also:

• https://stackoverflow.com/q/28909747/
• Please add TeX fonts for MathJax, not just STIX-web (or make it very easy for end-users to do so) #2536

I'm not sure whether this PR uses the right/best way to do this, but it works for me when I try it locally.

In an unrelated, later change, it would of course also be great to upgrade to MathJax version 3, see #5758.

[afshin]

@mgeier Could you please attach a couple screenshots to show the difference that this change makes in some representative notebooks?

cc: @vidartf @isabela-pf

[mgeier]

It looks like in the meantime the situation has magically improved on its own (at the MathJax side I guess?).

Previously, bold symbols -- especially when decorated with \boldsymbol{\hat{...}} or something -- looked hideous. But now that has become much better.

The remaining differences are quite subtle.

Could you please attach a couple screenshots to show the difference that this change makes

Here's one example that caught my eye:

$a/b$

before:

after:

---

I still think it's worth switching, but the difference isn't that big anymore.

[jtpio]

The corresponding PR in JupyterLab was closed with the following comment: jupyterlab/jupyterlab#9907 (comment)

I think this becomes obsolete once JupyterLab switches to MathJax 3

Closing since Notebook 7 is built on JupyterLab, and now depends on MathJax 3. Thanks all!