feat: added new docs

docusaurus/docs/Flutter/stream_chat_flutter/message_widget.mdx

@@ -2,4 +2,47 @@
 id: message_widget
 sidebar_position: 11
 title: MessageWidget
----
+---
+
+A Widget For Displaying Messages And Attachments
+
+### Background
+
+There are several things that need to be displayed with text in a message in a modern messaging app:
+attachments, highlights if the message is pinned, user avatars of the sender, etc.
+
+To encapsulate all of this functionality into one widget, the Flutter SDK contains a `MessageWidget`
+widget which provides these out of the box.
+
+### Basic Example (Modifying `MessageWidget` in `MessageListView`)
+
+Primarily, the `MessageWidget` is used in the `MessageListView`. To customize only a few properties
+of the `MessageWidget` without supplying all other properties, the `messageBuilder` builder supplies
+a default implementation of the widget for us to modify.
+
+```dart
+class ChannelPage extends StatelessWidget {
+  const ChannelPage({
+    Key key,
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: MessageListView(
+        messageBuilder: (context, details, messageList, defaultMessageWidget) {
+           return defaultMessageWidget.copyWith(
+             showThreadReplyIndicator: false,
+           );
+        },
+      ),
+
+    );
+  }
+}
+```
+
+### Building A Custom Attachment
+
+When a custom attachment type (location, audio, etc.) is sent, the MessageWidget also needs to know
+how to build it.