Added extra markup (#26030)

* Added extra markup

I found some js code which was not highlighted so I wrapped it in js code block,
secondly, I added the link to reach/router as it was confusing if its react/router or reach/router

* added the link to reach/router

* Update glossary.md

docs/docs/glossary.md

@@ -58,7 +58,7 @@ Client-side refers to operations that are performed by the user's browser in a [
 
 ### Client-side rendering
 
-The practice of using JavaScript to render pages on the [client-side](#client-side), as opposed to [server-side rendering](/docs/glossary/server-side-rendering/) alone. Gatsby uses [React](#react) and the `@reach/router` library to enhance HTML pages compiled at [build time](#build) to navigate site pages in a web browser without traditional page reloads, enabling performance techniques like preloading and [pre-fetching](/docs/routing/#performance-and-prefetching), [intersection observer and responsive `srcset`](/blog/2019-04-02-behind-the-scenes-what-makes-gatsby-great/#modern-apis-in-gatsby) for images, and more. See also: [routing](#routing), which is handled on the client-side in Gatsby by default.
+The practice of using JavaScript to render pages on the [client-side](#client-side), as opposed to [server-side rendering](/docs/glossary/server-side-rendering/) alone. Gatsby uses [React](#react) and the [`@reach/router`](https://reach.tech/router/) library to enhance HTML pages compiled at [build time](#build) to navigate site pages in a web browser without traditional page reloads, enabling performance techniques like preloading and [pre-fetching](/docs/routing/#performance-and-prefetching), [intersection observer and responsive `srcset`](/blog/2019-04-02-behind-the-scenes-what-makes-gatsby-great/#modern-apis-in-gatsby) for images, and more. See also: [routing](#routing), which is handled on the client-side in Gatsby by default.
 
 ### CMS