docs: update plugins page (#5768)

Author: yannbf

docs/guide/using-plugins.md

@@ -4,4 +4,6 @@ title: Using Plugins | Guide
 
 # Using Plugins
 
-Vitest can be extended using plugins...
+Vitest can be extended using plugins, similar to how Vite plugins work. This allows you to enhance and customize Vitest's functionality by using the same API and concepts of Vite plugins.
+
+For detailed guidance on how to write plugins, you can refer to the [Vite plugin documentation](https://vitejs.dev/guide/api-plugin).