Add recma-nextjs-static-props to list of plugins

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

Closes GH-2033.

docs/docs/extending-mdx.server.mdx

@@ -68,6 +68,9 @@ You can use this template:
 See also the [list of remark plugins][remark-plugins] and
 [list of rehype plugins][rehype-plugins].
 
+*   [`remcohaszing/recma-nextjs-static-props`](https://github.com/remcohaszing/recma-nextjs-static-props)
+    — generate [`getStaticProps`](https://nextjs.org/docs/basic-features/data-fetching/get-static-props)
+    exposing top level identifiers in Next.js
 *   [`remcohaszing/rehype-mdx-title`](https://github.com/remcohaszing/rehype-mdx-title)
     — expose the page title as a string
 *   [`remcohaszing/remark-mdx-code-meta`](https://github.com/remcohaszing/remark-mdx-code-meta)