docs: Added reminder for menu import to rendition menu docs (#1003)

I did not just lose 4 hours of my life trying to find out why the
rendition menu wasn't working 🥲

To prevent someone else from making the same mistake, I added this
warning. Copied it from other menu pages that already included this
warning, which I only encountered after reverse engineering how the menu
works myself 😅

Hope it's helpful to at least one person out there!

docs/src/pages/docs/en/components/media-rendition-menu.mdx

@@ -9,6 +9,13 @@ import SandpackContainer from "../../../../components/SandpackContainer.astro";
 
 A menu for video renditions (qualities).
 
+> Remember to add the seperate menu module for the menu components.
+
+```js
+import "media-chrome";
+import "media-chrome/menu";
+```
+
 ### Default usage
 
 <SandpackContainer