[discussion] compatibility with other plugins related to `remark`

[JounQin]

@btmills Hi, #179 is not related, at this PR actually only adds blocksCache and getShortLang and better TypeScript support.

For blocksCache, it is actually an issue described at #178 (comment)

For getShortLang, it fixes #176

For ts typings generated by typescript + jsdoc, it will be easier to be resued in eslint-mdx. I can just copy-paste the source code of eslint-plugin-markdown into https://github.com/mdx-js/eslint-mdx/blob/master/packages/eslint-plugin-mdx/src/processors/markdown.ts for now.

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I added eslint-plugin-mdx as dev dep just to make sure they are working compatibly.

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Originally posted by @JounQin in #178 (comment)

[JounQin]

continue to discuss on PR instead