feat(core): support MDX

[elijah-potter]

Issues

Closes #2702

Description

This PR adds support for MDX by replacing the existing pulldown_cmark-based Markdown parser with one based on the markdown crate, which already supports MDX.

How Has This Been Tested?

Existing tests pass. I will be adding more tests that include MDX.

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.

[FoxxMD]

An easy win! It seems. Hoping this can get merged soon so I can start linting all my documentation 😄

[elijah-potter]

The problem we've encountered that's made this work difficult to merge, is that our fuzzer found several high-profile panic conditions in the upstream crate used by this PR (markdown). It doesn't seem maintained, which makes it a difficult dependency to add. I'm thinking through solutions, though. Hopefully, we can merge it soon.