Is there an existing issue for this?

• I have searched the existing issues
• I have read the guide to filing a bug

Use case

Unlike DateTime, TimeOfDay does not have compareTo() method.
In order to compare 2 TimeOfDay objects, you have to use this awkward way:

1. Create a helper extension:

extension TimeOfDayExt on TimeOfDay {
  /// note: 'hour' is in 24-hour format
  double toDouble() => hour + minute/60.0;
}

2. Convert both TimeOfDay's to double:

    final double nowTime = TimeOfDay.now().toDouble();
    final double deadlineTime = TimeOfDay.fromDateTime(deadline).toDouble();

3. Compare these doubles:

if (nowTime >= deadlineTime) {
    // you're fired
}

Proposal

Add a compareTo() method for TimeOfDay, so we can compare them directly.