docs: update import user guide text + add diagram in brand module guide (#12385)

www/apps/book/app/learn/customization/custom-features/module/page.mdx

@@ -10,6 +10,8 @@ A module is a reusable package of functionalities related to a single domain or
 
 In a module, you create data models and business logic to manage them. In the next chapters, you'll see how you use the module to build commerce features.
 
+![Diagram showcasing an overview of the Brand Module](https://res.cloudinary.com/dza7lstvk/image/upload/v1746546820/Medusa%20Resources/brand-module_pg86gm.jpg)
+
 <Note>
 
 Learn more about modules in [this chapter](../../../fundamentals/modules/page.mdx).