docs: general fixes and overall changes (#7258)

* editing halfway

* edited second half

* adjust starter steps

* fix build

* typo fix

www/apps/book/app/advanced-development/admin/widgets/page.mdx

@@ -24,7 +24,7 @@ For example, you can add a widget on the order details page that shows payment d
 
 ## How to Create a Widget?
 
-A widget is created in a file under the `src/admin/widgets` directory. The file’s default export must be the widget, which is the React component, and must also export the widget’s configurations.
+A widget is created in a file under the `src/admin/widgets` directory. The file’s default export must be the widget, which is the React component. The file must also export the widget’s configurations.
 
 For example, create the file `src/admin/widgets/product-widget.tsx` with the following content: