toText method
Return duration string in '00:00' format
Implementation
String toText() {
String twoDigits(int n) => n.toString().padLeft(2, '0');
final twoDigitMinutes = twoDigits(inMinutes.remainder(60));
final twoDigitSeconds = twoDigits(inSeconds.remainder(60));
return '$twoDigitMinutes:$twoDigitSeconds';
}