feat: Send image / video / file dialog

lib/utils/matrix_file_extension.dart

@@ -31,4 +31,34 @@ extension MatrixFileExtension on MatrixFile {
     }
     return;
   }
+
+  MatrixFile get detectFileType {
+    if (msgType == MessageTypes.Image) {
+      return MatrixImageFile(bytes: bytes, name: name);
+    }
+    if (msgType == MessageTypes.Video) {
+      return MatrixVideoFile(bytes: bytes, name: name);
+    }
+    if (msgType == MessageTypes.Audio) {
+      return MatrixAudioFile(bytes: bytes, name: name);
+    }
+    return this;
+  }
+
+  String get sizeString {
+    var size = this.size.toDouble();
+    if (size < 1000000) {
+      size = size / 1000;
+      size = (size * 10).round() / 10;
+      return '${size.toString()} KB';
+    } else if (size < 1000000000) {
+      size = size / 1000000;
+      size = (size * 10).round() / 10;
+      return '${size.toString()} MB';
+    } else {
+      size = size / 1000000000;
+      size = (size * 10).round() / 10;
+      return '${size.toString()} GB';
+    }
+  }
 }