feat: support math formula

[usoonees]

fix: #1223 #1802

1. add rehypeKatex plugin to support latex syntax.
2. replace \(..\) and \[...\] to $...$ and $$...$$.

Due to remark-math only supporting the use of the $ symbol for inline math and $$ for block math (see discussion at: remarkjs/remark-math#39), we need to convert math notations from \(..\) to $...$ and from \[...\] to $$...$$ .

After:

Before

[xl0]

@usoonees I tried this approach for my project, don't think this is the way to go, there are too many corner-cases.
I think we should write a replacement for remark-math / mdast-util-math to handle them properly.

[xl0]

For example:

• LLMs that use the bracket syntax will not escape $ in text, so $100 to $200 will be seen as a formula.
• LLMs will produce \[ ... \] without new lines, and use syntax that is only allowed in block math inside. This is parsed as inline math, and gives a rendering error.
• Math inside
  • Deeply
    • Nested
      • Lists

requires special handling, as

      $$
      \formula
$$

is not handled correctly.

Another concern, this project is kinda dead, if you consider the number of open PRs and lack of action. I used to host chatbot-ui for myself and friends, but am now working on Congusto Chat, which will soon reach feature parity, and has an ambitious roadmap, including code interpreter and artefacts.