add tutorial docs in examples

example/lib/multiple_conversation.dart

@@ -1,12 +1,32 @@
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
+/// Second step of the [tutorial](https://getstream.io/chat/flutter/tutorial/)
+///
+/// Most chat applications handle more than just one single conversation.
+/// Apps like Facebook Messenger, Whatsapp and Telegram allows you to have multiple one to one and group conversations.
+///
+/// Let’s find out how we can change our application chat screen to display the list of conversations and navigate between them.
+///
+/// > Note: the SDK uses Flutter’s [Navigator] to move from one route to another, this allows us to avoid any boiler-plate code.
+/// > Of course you can take total control of how navigation works by customizing widgets like [Channel] and [ChannelList].
+///
+/// If you run the application, you will see that the first screen shows a list of conversations, you can open each by tapping and go back to the list.
+///
+/// Every single widget involved in this UI can be customized or swapped with your own.
+///
+/// The [ChannelListPage] widget retrieves the list of channels based on a custom query and ordering.
+/// In this case we are showing the list of channels the current user is a member and we order them based on the time they had a new message.
+/// [ChannelListView] handles pagination and updates automatically out of the box when new channels are created or when a new message is added to a channel.
 void main() async {
-  final client = Client('s2dxdhpxd94g', logLevel: Level.INFO);
+  final client = Client(
+    'b67pax5b2wdq',
+    logLevel: Level.INFO,
+  );
 
   await client.setUser(
-    User(id: 'still-resonance-3'),
-    'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyX2lkIjoic3RpbGwtcmVzb25hbmNlLTMifQ.e6BGSX21gLZYpls_rFX8PB2SfGlfdpvv00pQiVW70VQ',
+    User(id: 'falling-mountain-7'),
+    'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyX2lkIjoiZmFsbGluZy1tb3VudGFpbi03In0.AKgRXHMQQMz6vJAKszXdY8zMFfsAgkoUeZHlI-Szz9E',
   );
 
   runApp(MyApp(client));