add stream chat theme draft

lib/src/channel_image.dart

@@ -1,16 +1,17 @@
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
+import 'package:stream_chat_flutter/stream_chat_flutter.dart';
 
 class ChannelImage extends StatelessWidget {
   const ChannelImage({
     Key key,
     @required this.channel,
-    this.radius = 20,
+    this.size = 40,
   }) : super(key: key);
 
   final Channel channel;
-  final double radius;
+  final double size;
 
   @override
   Widget build(BuildContext context) {
@@ -18,16 +19,32 @@ class ChannelImage extends StatelessWidget {
         stream: channel.extraDataStream,
         initialData: channel.extraData,
         builder: (context, snapshot) {
-          return CircleAvatar(
-            radius: radius,
-            backgroundImage: snapshot.data?.containsKey('image') ?? false
-                ? CachedNetworkImageProvider(snapshot.data['image'])
-                : null,
+          return Container(
+            padding: const EdgeInsets.all(4),
+            constraints: StreamChatTheme.of(context)
+                .channelPreviewTheme
+                .avatarTheme
+                .constraints,
+            decoration: BoxDecoration(
+              borderRadius: StreamChatTheme.of(context)
+                  .channelPreviewTheme
+                  .avatarTheme
+                  .borderRadius,
+              color: StreamChatTheme.of(context).accentColor,
+            ),
             child: snapshot.data?.containsKey('image') ?? false
-                ? null
-                : Text(snapshot.data?.containsKey('name') ?? false
-                    ? snapshot.data['name'][0]
-                    : ''),
+                ? CachedNetworkImage(
+                    imageUrl: snapshot.data['image'],
+                    errorWidget: (_, __, ___) {
+                      return Center(
+                        child: Text(snapshot.data?.containsKey('name') ?? false
+                            ? snapshot.data['name'][0]
+                            : ''),
+                      );
+                    },
+                    fit: BoxFit.cover,
+                  )
+                : SizedBox(),
           );
         });
   }