How to include markdown file (md) inside mdx file

plain.md

# plain markdown

some.mdx

# some mdx file

include './plain.md'

Result file

# some mdx file

# plain markdown

How to do something like this with mdxjs?

Oh, that's actually right in their docs. Was known as transclusion some time ago.

import License from './license.md'
import Contributing from './docs/contributing.mdx'

# Hello, world!

<License />

---

<Contributing />