docs: improve admin documentation (#6117)

- Move the admin plugin's options to the Admin Configuration documentation.
- Add a section on how to change the backend URL for both development and production.
- Fix the troubleshooting section related to port forwarding.
- General fixes.

www/apps/docs/content/development/entities/extend-repository.md

@@ -54,7 +54,9 @@ export const ProductRepository = dataSource
   .extend({
     // it is important to spread the existing repository here.
     //  Otherwise you will end up losing core properties
-    ...Object.assign(MedusaProductRepository, { target: Product }),
+    ...Object.assign(MedusaProductRepository, {
+      target: Product,
+    }),
 
     /**
      * Here you can create your custom function