Recover rehype-katex css link example updating the version. Update

modified date of page.

docs/guides/math.mdx

@@ -5,7 +5,7 @@ export const info = {
     {name: 'Titus Wormer', github: 'wooorm', twitter: 'wooorm'}
   ],
   published: new Date('2021-10-06'),
-  modified: new Date('2022-12-14')
+  modified: new Date('2023-10-09')
 }
 
 # Math
@@ -68,6 +68,11 @@ console.log(
 <Note type="important">
   **Important**: if you chose `rehype-katex`, you should also use `katex.css`
   somewhere on the page to style math properly.
+  At the time of writing, the last version is:
+  ```html
+  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.9/dist/katex.min.css" integrity="sha384-n8MVd4RsNIU0tAv4ct0nTaAbDJwPJzDEaqSD1odI+WdtXRGWt2kTvGFasHpSy3SV" crossorigin="anonymous">
+  ```
+
   To get the latest link to the stylesheet, go to [`katex docs`][katex docs].
 </Note>