docs: revise main docs outline (#10502)

www/apps/book/app/learn/customization/customize-admin/widget/page.mdx

@@ -59,7 +59,7 @@ You'll now add a widget to the product-details page. A widget is a React compone
 
 <Note>
 
-Learn more about widgets in [this documentation](../../../advanced-development/admin/widgets/page.mdx).
+Learn more about widgets in [this documentation](../../../fundamentals/admin/widgets/page.mdx).
 
 </Note>