docs: add notes + missing links for user guide (#11621)

* docs: add notes + missing links for user guide

* fix build errors

* fixes

www/apps/resources/app/storefront-development/cart/create/page.mdx

@@ -107,8 +107,6 @@ export const highlights = [
   </CodeTab>
 </CodeTabs>
 
-{/* TODO add a link to cart object in API reference (once available). */}
-
 The response of the Create Cart API route has a `cart` field, which is a cart object.
 
 Refer to the [Create Cart API reference](!api!/store#carts_postcarts) for details on other available request parameters.

www/apps/resources/app/storefront-development/cart/retrieve/page.mdx

@@ -118,9 +118,7 @@ export const highlights = [
   </CodeTab>
 </CodeTabs>
 
-{/* TODO add a link to cart object in API reference (once available). */}
-
-The response of the Retrieve Cart API route has a `cart` field, which is a cart object.
+The response of the [Get Cart API](!api!/store#carts_getcartsid) route has a `cart` field, which is a cart object.
 
 ---