readTag method
Reads a NbtTag from fileReader.
If the parent is a NbtList or NbtArray, withName should be set to false to avoid reading
the name of this Tag.
Implementation
@override
NbtInt readTag(NbtReader nbtReader, {bool withName = true}) {
  final name = withName ? nbtReader.readString() : 'None';
  final value = nbtReader.readInt(signed: true);
  return this
    ..name = name
    .._value = value;
}