docs(guides/mdx): mention including highlight.js css file (#4571)

Co-authored-by: Mehdi Achour <[email protected]>
Co-authored-by: Michaël De Boey <[email protected]>

Author: 3 people

contributors.yml

@@ -177,6 +177,7 @@
 - dunglas
 - dvargas92495
 - dwightwatson
+- dwjohnston
 - dwt47
 - dylanplayer
 - eastlondoner

docs/guides/mdx.md

@@ -204,8 +204,12 @@ exports.mdx = async (filename) => {
 };
 ```
 
+The above configuration parses the markdown to insert [highlight.js][highlightjs] friendly DOM elements. To have the syntax highlighting appear, you will also need to include the highlight.js css file. See also [surfacing styles][surfacing-styles].
+
 [mdx-plugin]: https://mdxjs.com/packages/rollup
 [mdx]: https://mdxjs.com
 [yaml]: https://yaml.org
 [mdx-bundler]: https://github.com/kentcdodds/mdx-bundler
 [classic-remix-compiler]: ./vite#classic-remix-compiler-vs-remix-vite
+[surfacing-styles]: ../styling#surfacing-styles
+[highlightjs]: https://highlightjs.org/