Allow ability to pass scope to MDX document

It’d be nice to be able pass in additional components and props to the component scope.

import React from 'react'
import { Box } from './ui'
import Document from './doc.md'

export default () => <Document scope={{ title: 'Hello', Box }} />

# This is some markdown

That has `Box` and `title` in scope:

<Box>{title}</Box>

[fabe]

We thought about giving MDX files to editors of a website. Having them import components from a remote location doesn’t sound particularly usable or safe, so we wondered if we could handle the imports at build time.

Docs for a custom loader would be very appreciated!

[johno]

I def hear you there. Probably isn’t the best solution.

I’ve run into this once so far on a project (basically wanted to add scope to a collection of MDX documents without having to explicitly import), but I ended up writing a custom loader.

I wonder if we perhaps write up a doc instead on how to write your own MDX loader? There isn’t much to the loader itself since all the logic/transpilation is in core.