EitherOrd<A, B> class

A class that extends Ord to provide a custom ordering for Either values.

This class provides a way to compare two Either values based on the provided orderings for the Left and Right types.

If both Either values are Left, they are compared using the provided leftOrd. If both are Right, they are compared using the provided rightOrd.

If one is Left and the other is Right, Left is considered to come before Right.

Example usage:

final intOrder = Ord<int>((a, b) => a.compareTo(b));
final strOrder = Ord<String>((a, b) => a.compareTo(b));

final eitherOrder = EitherOrd(intOrder, strOrder);

final e1 = Left<int, String>(3);
final e2 = Left<int, String>(5);
final e3 = Right<int, String>("apple");
final e4 = Right<int, String>("banana");

print(eitherOrder.compare(e1, e2)); // -1 because 3 < 5
print(eitherOrder.compare(e3, e4)); // -1 because "apple" < "banana"
print(eitherOrder.compare(e1, e3)); // -1 because Left always comes before Right