Document usage in flat config

[levino]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Problem

It is unclear how to use this package with the new eslint flat config.

Solution

Provide documentation on how to use this package with an eslint flat config. Potentially one would have to show how to use the backwards compatibility tool until the exports of this library have been changed.

Alternatives

I would say no.

[JounQin]

Basically, it should be something like following:

// eslint.config.js

import * as eslintMdx from 'eslint-mdx'
import * as mdx from 'eslint-plugin-mdx'

export default [
  {
    files: ['**/*.mdx'],
    plugins: {
      mdx,
    },
    languageOptions: {
      parser: eslintMdx,
    },
    processor: mdx.processors.remark,
    settings: {
      'mdx/code-blocks': true, // this won't work sadly
    },
    rules: {
      'no-console': 'error',
    },
  },
]

We're blocked by eslint/eslint#12068