added description for each InvoiceItem

Author: itskawsar

src/Classes/InvoiceItem.php

@@ -16,6 +16,11 @@ class InvoiceItem
      */
     public $title;
 
+    /**
+     * @var string|bool
+     */
+    public $description = false;
+
     /**
      * @var string
      */
@@ -77,6 +82,17 @@ public function title(string $title)
         return $this;
     }
 
+    /**
+     * @param string $description
+     * @return $this
+     */
+    public function description(string $description)
+    {
+        $this->description = $description;
+
+        return $this;
+    }
+
     /**
      * @param string $units
      * @return $this