Could we add EitherX ?

[CorentinClabaut]

I guess we could have:

type Either3[T1 any, T2 any, T3 any] struct {
	argId int

	arg1 T1
	arg2 T2
	arg3 T3
}

Constructors:

mo.CreateEither3Arg1() mo.CreateEither3Arg2() mo.CreateEither3Arg3()

Methods:

.IsArg(i int) .Arg1() .Arg2() .Arg3() .MustArg1() .MustArg2() .MustArg3() .Arg1OrElse() .Arg2OrElse() .Arg3OrElse() .Arg1OrEmpty() .Arg2OrEmpty() .Arg3OrEmpty() .ForEach() .Match() .MapArg1() .MapArg2() .MapArg3()

@samber If you agree that it could be useful I could add Either3/4/5 If this is added I'm wondering if we should then have Either2 instead of the current Either type for consistency? And maybe mark the current Either as deprecated?