Export the original latex format in html

[Eggslegend]

I'm wondering if the latex format can be saved and shown correctly when exporting to html.
Here are the examples.

ChatGPT-Sine_Formula_Explanation.json

[pionxzh]

I think we can try to include latex.js or generate the image embedded. Are you interested in submitting a PR?

[moonmd]

The new commit is a70a8b1 feat: html enhancements: toggle width & latex rendering
There are new package requirements and some modest upgrades in this commit.
I did clone a clean repo and verified the build and functional tests.

Text from the original PR:

1. Added a second toggle for widescreen view
2. Added katex to template.html to render latex. (This is the same engine OpenAI uses.)

The default render was not very readable but after some experimentation I found a format close to the original by adding \displaystyle and \large macros to the preprocessor.

Bare css was not able to center the display math (vs. inline) because identical css is generated for both. I check the nodes on either side of the latex parent for text to determine if it is inline and apply the proper formatting.

[moonmd]

Final PR #275