Add support for shipping dimensions (#29)

Author: jakeday

src/Product.php

@@ -367,6 +367,51 @@ public function setShippingWeight($str)
         return $this;
     }
 
+    /**
+     * Add shipping length
+     * 
+     * @see https://support.google.com/merchants/answer/6324498?hl=en
+     * 
+     * @param string $str
+     *
+     * @return $this
+     */
+    public function setShippingLength($str)
+    {
+        $this->setAttribute('shipping_length', $str, false);
+        return $this;
+    }
+
+    /**
+     * Add shipping width
+     * 
+     * @see https://support.google.com/merchants/answer/6324498?hl=en
+     * 
+     * @param string $str
+     *
+     * @return $this
+     */
+    public function setShippingWidth($str)
+    {
+        $this->setAttribute('shipping_width', $str, false);
+        return $this;
+    }
+
+    /**
+     * Add shipping height
+     * 
+     * @see https://support.google.com/merchants/answer/6324498?hl=en
+     * 
+     * @param string $str
+     *
+     * @return $this
+     */
+    public function setShippingHeight($str)
+    {
+        $this->setAttribute('shipping_height', $str, false);
+        return $this;
+    }
+
     /**
      * Set a custom label
      *