update dependencies (install Docusaurus 3)

[elevatebart]

• Update all dependencies (prettier, docusaurus, remark, unist,... )
• Rewrite the MDX plugins for compat with updated version of remark
• Use sync version of prettier as prettier has become async
• Remove all MDX1 hacks from the codebase

Caveat: some customized header hashes cannot be parsed in DS3. See Yields has disapeared here. The end result seems the same. so I am not worried.

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[jaffrepaul]

I'm good with all this. Nice job working through the remark stuff 💪

Two q's just for my edification:

• Why does the prettier need to work sync?
• I didn't quite understand the header hashes caveat you mentioned. Did something not translate in v3?

[elevatebart]

I'm good with all this. Nice job working through the remark stuff 💪

Two q's just for my edification:

• Why does the prettier need to work sync?

The visit function that remark is using to change the content and load the config files for instance needs to use visitors that are synchronous. The maintainer or remark and MDX is very convinced of it. If a function is async, any function that depends on it needs to be async too. So we cannot use prettier.format if it's async. Believe me I tried. Good thing there is a @prettier/sync library maintained by the prettier team already.

• I didn't quite understand the header hashes caveat you mentioned. Did something not translate in v3?

Before, when an icon was in a header, the Icon name was made part of the ID. We went around it with adding stuff at the end of header lines.

### Yields [<IconHelp>](https://example-docs.org/yields) {#Yields}
                                                          ^^^^^^^

Problem is: on some pages the "acorn" parser did not like it one bit. I removed it where it was problematic and the hash have not changed. The one above for instance is still "Yields"