[Channel List Header] Replace pen_write icon with correct svg icon.

images/icon_pen-write.svg

@@ -0,0 +1,5 @@
+<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
+    <path fill-rule="evenodd" clip-rule="evenodd"
+        d="M21 21H3V16.757L16.435 3.322C16.8255 2.93162 17.4585 2.93162 17.849 3.322L20.678 6.151C21.0684 6.5415 21.0684 7.1745 20.678 7.565L9.243 19H21V21ZM5 19H6.414L15.728 9.686L14.314 8.272L5 17.586V19ZM18.556 6.858L17.142 8.272L15.728 6.858L17.142 5.444L18.556 6.858Z"
+        fill="#006CFF" />
+</svg>

lib/src/channel_list_header.dart

@@ -1,6 +1,7 @@
 import 'dart:ui';
 
 import 'package:flutter/material.dart';
+import 'package:flutter_svg/flutter_svg.dart';
 import 'package:stream_chat/stream_chat.dart';
 import 'package:stream_chat_flutter/src/stream_neumorphic_button.dart';
 import 'package:stream_chat_flutter/stream_chat_flutter.dart';
@@ -107,8 +108,11 @@ class ChannelListHeader extends StatelessWidget implements PreferredSizeWidget {
                     color = Colors.grey;
                     break;
                 }
-                return Icon(
-                  StreamIcons.pen_write,
+                return SvgPicture.asset(
+                  'images/icon_pen-write.svg',
+                  package: 'stream_chat_flutter',
+                  width: 24.0,
+                  height: 24.0,
                   color: color,
                 );
               },