Added the Cart Resource

The Cart resource is read only, where you would provide the cart_token to retrieve the cart object.
Example: `$shopify->Cart('ea4a55031cbbcd5621918d3a893869b0')->get()`

You can retrieve the cart token on your website by using the following javascript snippet `var cart_token = document.cookie.match('(^|; )cart=([^;]*)');`

Author: whobutsb

README.md

@@ -302,7 +302,8 @@ Some resources are available directly, some resources are only available through
 - Blog -> Article -> [Metafield](https://help.shopify.com/api/reference/metafield)
 - Blog -> [Event](https://help.shopify.com/api/reference/event/)
 - Blog -> [Metafield](https://help.shopify.com/api/reference/metafield)
-- [CarrierService](https://help.shopify.com/api/reference/carrierservice/)
+- [CarrierService](https://help.shopify.com/api/reference/carrierservice/)-
+- [Cart](https://shopify.dev/docs/themes/ajax-api/reference/cart) (read only)
 - [Collect](https://help.shopify.com/api/reference/collect/)
 - [Comment](https://help.shopify.com/api/reference/comment/)
 - Comment -> [Event](https://help.shopify.com/api/reference/event/)

lib/Cart.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace PHPShopify;
+
+/* @see https://shopify.dev/docs/themes/ajax-api/reference/cart */
+use PHPShopify\ShopifyResource;
+
+class Cart extends ShopifyResource {
+
+     /**
+     * @inheritDoc
+     */
+    protected $resourceKey ='cart';
+
+     /**
+     * @inheritDoc
+     */
+    public $searchEnabled = false;
+
+     /**
+     * @inheritDoc
+     */
+    public $readOnly = true;
+}

lib/ShopifySDK.php

@@ -71,6 +71,7 @@
  * @property-read ApplicationCharge $ApplicationCharge
  * @property-read Blog $Blog
  * @property-read CarrierService $CarrierService
+ * @property-read Cart $Cart
  * @property-read Collect $Collect
  * @property-read Collection $Collection
  * @property-read Comment $Comment
@@ -115,6 +116,7 @@
  * @method ApplicationCharge ApplicationCharge(integer $id = null)
  * @method Blog Blog(integer $id = null)
  * @method CarrierService CarrierService(integer $id = null)
+ * @method Cart Cart(string $cart_token = null)
  * @method Collect Collect(integer $id = null)
  * @method Collection Collection(integer $id = null)
  * @method Comment Comment(integer $id = null)
@@ -167,6 +169,7 @@ class ShopifySDK
         'ApplicationCharge',
         'Blog',
         'CarrierService',
+        'Cart',
         'Collect',
         'Collection',
         'Comment',