docs: general updates to documentation pages (#13128)

www/apps/resources/app/admin-components/components/header/page.mdx

@@ -10,6 +10,8 @@ export const metadata = {
 
 # {metadata.title}
 
+In this guide, you'll learn how to create a header component that matches the Medusa Admin's design conventions.
+
 Each section in the Medusa Admin has a header with a title, and optionally a subtitle with buttons to perform an action.
 
 ![Example of a header in a section](https://res.cloudinary.com/dza7lstvk/image/upload/v1728288562/Medusa%20Resources/header_dtz4gl.png)