adds GraphQLList to the imports when mentioned

Noticed that GraphQLList was being used but not imported in the first example. Looking forward to using this example at work to as part of some research and development I am doing at work

Author: bdougie

site/blog/20160502-rest-api-graphql-wrapper.md

@@ -51,6 +51,7 @@ Each field will consist of a return type, optional argument definitions, and a J
 
 ```js
 import {
+  GraphQLList,
   GraphQLObjectType,
   GraphQLString,
 } from 'graphql';