Documentation comparing math plugins

[coreylionis]

After two days of hard work, I managed to get .mdx documents with Katex segments to render correctly using gatsby-plugin-mdx extended with gatsby-remark-katex. This process was confounded by the lack of a clear recommendation or comparison across various forums and template sites: some people recommend remark-math and rehype-katex, some recommend gatsby-remark-katex, and there is also a gatsby-transformer-katex. Gatsby-remark-katex first worked for me once I had updated gatsby-config and gatsby-node to ESM, but this wasn't mentioned in the discussions of gatsby-remark-katex I found.

It seems that gatsby-remark-katex is the supported version, and mdx compatibility means it aligns with the tutorial documentation.
I think it would be best to consolidate current information about choosing a math parser into a separate blog post: recommendations would cover basic setups which are known to work/not to work, and which to preference over the other.

(it would also be nice to get some insight on gatsby-plugin-mdx not accepting remark-math and rehype-katex within mdxoptions. Using the GraphiQL layer I found that the strict : ignore option passed with rehypeKatex was associated with gatsby-plugin-mdx but the remark and rehype plugins were removed)