Implement comparator interface for CalendarDay

[ghost]

Feature

To add the CalendarDay object in a TreeSet, the Comparator interface implementation is required. Please implement this interface on CalendarDay object, based on LocalDate comparison.

[kizitonwose]

Why not use the TreeSet constructor that allows you to provide a comparator:

val set = TreeSet<CalendarDay> { d1, d2 ->
    d1.date.compareTo(d2.date)
}

[kizitonwose]

Closing this as it is not necessary to implement it in the library.