feat: Added new docs

docusaurus/docs/Flutter/stream_chat/searching_messages.mdx

@@ -4,3 +4,28 @@ sidebar_position: 20
 title: Searching Messages
 ---
 
+Message search is built-in to the chat API. You can enable and/or disable the search indexing on a per channel type.
+The command shown below selects the channels in which John is a member.
+Next, it searches the messages in those channels for the keyword “'supercalifragilisticexpialidocious'”:
+
+```dart
+final search = await client.search(
+    Filter.in_('members', ['john']),
+    query: 'supercalifragilisticexpialidocious',
+    paginationParams: PaginationParams(
+        limit: 2,
+        offset: 0
+    ),
+);
+```
+
+Pagination works via the standard limit and offset parameters. The first argument, filter, uses a MongoDB style query expression.
+
+We do not run MongoDB on the backend, so only a subset of the standard MongoDB filters are supported.
+Additionally, this endpoint can be used to search for messages that have attachments.
+
+```dart
+// Search file of type videos
+  final response = await channel.search(messageFilter: Filter.in_('attachments.type', ['video']));
+  return response;
+```