fix: add relevant information to storybook simple sample

Author: sravan-s

src/smart-components/NotificationChannel/stories/index.stories.js

@@ -1,11 +1,15 @@
-import React, { useState, useCallback } from 'react';
+import React from 'react';
 
 import Sendbird from '../../../lib/Sendbird';
 import NotificationChannel from '../index';
 import { TestApp } from './TestApp';
 
 export default { title: 'NotficationChannel' };
 
+const appId = '';
+const userId = '';
+const accessToken = '';
+
 export const NotificationChannelComponent = () => (
   <Sendbird
     appId={appId}
@@ -14,7 +18,7 @@ export const NotificationChannelComponent = () => (
   >
     <div style={{ height: '500px', width: '360px' }}>
       <NotificationChannel
-        channelUrl='SENDBIRD_NOTIFICATION_CHANNEL_NOTIFICATION_sravan'
+        channelUrl={`SENDBIRD_NOTIFICATION_CHANNEL_NOTIFICATION_${userId}`}
       />
     </div>
   </Sendbird>