add TODO for send event request content to be Content

lib/models/requests/send_event_request.dart

@@ -7,6 +7,7 @@ abstract class SendEventRequest with _$SendEventRequest {
   const factory SendEventRequest({
     required String roomId,
     required String type,
+    // TODO: Make this a type of `Content`, will need changes for sending reactions
     required Map<String, dynamic> content,
     @Default(false) bool synchronous,
     @Default(false) bool disableEncryption,