Add remark-mdx-math-enhanced to list of plugins

Closes GH-2028.

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>
Reviewed-by: Titus Wormer <tituswormer@gmail.com>

docs/docs/extending-mdx.server.mdx

@@ -76,6 +76,8 @@ See also the [list of remark plugins][remark-plugins] and
     — change image sources to JavaScript imports
 *   [`remcohaszing/remark-mdx-frontmatter`](https://github.com/remcohaszing/remark-mdx-frontmatter)
     — change frontmatter (YAML) metadata to exports
+*   [`goodproblems/remark-mdx-math-enhanced`](https://github.com/goodproblems/remark-mdx-math-enhanced)
+    — enhance math with JavaScript inside it
 
 {/*
 please use alpha sorting on **project** name!

docs/guides/math.server.mdx

@@ -79,6 +79,13 @@ async function main() {
   ```
 </Note>
 
+<Note type="info">
+  **Note:** see also
+  [`remark-mdx-math-enhanced`](https://github.com/goodproblems/remark-mdx-math-enhanced),
+  which you can use to support JavaScript expressions inside of math (such as to
+  access props or to make calculations)
+</Note>
+
 [commonmark]: https://spec.commonmark.org/current/
 
 [remark-math]: https://github.com/remarkjs/remark-math/tree/main/packages/remark-math