chore: Add MDX renderer for Markdown with JSX support

[Bryan0324]

What does it do?

This pull request adds support for MDX (.mdx files) rendering to Hexo, enabling users to write blog posts and pages using MDX - a powerful combination of Markdown and JSX.

Features:

• Markdown Support: Full CommonMark markdown syntax support for content creation
• JSX Components: Embed and use React/Preact components directly in markdown
• JavaScript Expressions: Evaluate JavaScript expressions dynamically within content
• Custom Components: Define and use custom reusable components
• Inline Styles: Support for inline CSS styling with JavaScript objects
• Error Handling: Comprehensive error messages with file path information for debugging

Implementation:

• Uses @mdx-js/mdx v3.1.1 for MDX compilation
• Preact for lightweight JSX rendering
• Async rendering for non-blocking operations
• Nunjucks disabled for MDX files to prevent conflicts
• Registered as .mdx file extension handler

Example Usage:

Users can now create source/_posts/my-post.mdx with content like:

# Welcome to MDX

This is **markdown** with <span style={{color: 'red'}}>JSX</span>!

export const Button = ({text}) => (
  <button className="btn">{text}</button>
);

The answer is: {2 + 2 * 10}

<Button text="Click me!" />

Screenshots

N/A - Code feature (no UI changes)

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[github-actions]

How to test

git clone -b new_feature https://github.com/Bryan0324/hexo.git
cd hexo
npm install
npm test

[D-Sketon]

I think this should be independently implemented as a separate npm package, similar to hexo-renderer-marked.

[Bryan0324]

Is it okay if I submit a similar PR to hexo-renderer-marked, or should I create a new package?

[D-Sketon]

Each renderer should focus on rendering just one type of file and not take on too many responsibilities. To make this work better, it's a good idea to create a separate package. For example, you could build your own dedicated renderer called hexo-renderer-mdx.

[Bryan0324]

Thanks for the clarification! That makes sense — I’ll create a separate package for this.