feat: add latexOnly option to disable AsciiMath support

[wendyyuchensun]

Summary

Adds a latexOnly boolean option (default false) to createMarkdownToReactParser and createTableOfContents. When true, the math extension skips AsciiMath entirely - the tokenizer regex matches only LaTeX delimiters, and backtick-delimited content is left as plain text.

Usage

Pass latexOnly: true to opt out of AsciiMath:

const parse = createMarkdownToReactParser({
  options: {
    latexDelimiter: 'bracket',
    latexOnly: true,
  },
  components,
});

// Pass the same value to createTableOfContents so heading math tokens
// are parsed consistently with the renderer
const toc = createTableOfContents(markdown, { latexOnly: true });

[wendyyuchensun]

先關掉，明天會另外按照新討論重發一條。
https://coseeing.slack.com/archives/C0AB10CARU3/p1777559989988339?thread_ts=1777528249.059519&cid=C0AB10CARU3