docs(ui): update code documentation and tutorials

packages/stream_chat_flutter/example/lib/tutorial_part_1.dart

@@ -1,4 +1,5 @@
 // ignore_for_file: public_member_api_docs
+// ignore_for_file: prefer_expression_function_bodies
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
@@ -67,10 +68,8 @@ class MyApp extends StatelessWidget {
   final Channel channel;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return MaterialApp(
-      // ignore: prefer_expression_function_bodies
       builder: (context, widget) {
         return StreamChat(
           client: client,

packages/stream_chat_flutter/example/lib/tutorial_part_2.dart

@@ -1,4 +1,6 @@
 // ignore_for_file: public_member_api_docs
+// ignore_for_file: prefer_expression_function_bodies
+
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
@@ -14,7 +16,7 @@ import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 /// > 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].
+/// customizing widgets like [StreamChannel] and [StreamChannelListView].
 ///
 /// 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.
@@ -56,7 +58,6 @@ class MyApp extends StatelessWidget {
   final StreamChatClient client;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return MaterialApp(
       builder: (context, child) => StreamChat(
@@ -92,6 +93,12 @@ class _ChannelListPageState extends State<ChannelListPage> {
     sort: const [SortOption('last_message_at')],
   );
 
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) => Scaffold(
         body: RefreshIndicator(

packages/stream_chat_flutter/example/lib/tutorial_part_3.dart

@@ -1,4 +1,5 @@
 // ignore_for_file: public_member_api_docs
+// ignore_for_file: prefer_expression_function_bodies
 import 'package:collection/collection.dart' show IterableExtension;
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
@@ -16,8 +17,8 @@ import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 /// and include the number of unread messages for each.
 ///
 /// We're passing a custom widget
-/// to [StreamChannelListView.channelPreviewBuilder];
-/// this will override the default [StreamChannelPreview] and allows you
+/// to [StreamChannelListView.itemBuilder];
+/// this will override the default [StreamChannelListTile] and allows you
 /// to create one yourself.
 ///
 /// There are a couple interesting things we do in this widget:
@@ -57,7 +58,6 @@ class MyApp extends StatelessWidget {
   final StreamChatClient client;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return MaterialApp(
       builder: (context, child) => StreamChat(
@@ -89,6 +89,12 @@ class _ChannelListPageState extends State<ChannelListPage> {
     limit: 20,
   );
 
+  @override
+  void dispose() {
+    _listController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) => Scaffold(
         body: StreamChannelListView(
@@ -160,7 +166,6 @@ class ChannelPage extends StatelessWidget {
   }) : super(key: key);
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: const StreamChannelHeader(),

packages/stream_chat_flutter/example/lib/tutorial_part_4.dart

@@ -1,4 +1,6 @@
 // ignore_for_file: public_member_api_docs
+// ignore_for_file: prefer_expression_function_bodies
+
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
@@ -43,7 +45,6 @@ class MyApp extends StatelessWidget {
   final StreamChatClient client;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return MaterialApp(
       builder: (context, child) => StreamChat(
@@ -75,6 +76,12 @@ class _ChannelListPageState extends State<ChannelListPage> {
     limit: 20,
   );
 
+  @override
+  void dispose() {
+    _listController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) => Scaffold(
         body: StreamChannelListView(
@@ -125,7 +132,6 @@ class ThreadPage extends StatelessWidget {
   final Message? parent;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: StreamThreadHeader(

packages/stream_chat_flutter/example/lib/tutorial_part_5.dart

@@ -1,4 +1,5 @@
 // ignore_for_file: public_member_api_docs
+// ignore_for_file: prefer_expression_function_bodies
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
@@ -47,7 +48,6 @@ class MyApp extends StatelessWidget {
   final StreamChatClient client;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return MaterialApp(
       builder: (context, child) => StreamChat(
@@ -79,6 +79,12 @@ class _ChannelListPageState extends State<ChannelListPage> {
     limit: 20,
   );
 
+  @override
+  void dispose() {
+    _listController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) => Scaffold(
         body: StreamChannelListView(
@@ -103,7 +109,6 @@ class ChannelPage extends StatelessWidget {
   }) : super(key: key);
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: const StreamChannelHeader(),

packages/stream_chat_flutter/example/lib/tutorial_part_6.dart

@@ -1,4 +1,6 @@
 // ignore_for_file: public_member_api_docs
+// ignore_for_file: prefer_expression_function_bodies
+
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
@@ -112,6 +114,13 @@ class _ChannelListPageState extends State<ChannelListPage> {
     sort: const [SortOption('last_message_at')],
     limit: 20,
   );
+
+  @override
+  void dispose() {
+    _listController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) => Scaffold(
         body: StreamChannelListView(
@@ -162,7 +171,6 @@ class ThreadPage extends StatelessWidget {
   final Message? parent;
 
   @override
-  // ignore: prefer_expression_function_bodies
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: StreamThreadHeader(