UWP Support: Add ScarletCommandManager that doesnt rely on WPFs CommandManager

[mastorm]

Microsoft removed the CommandManager in UWP.

https://github.com/Insire/MvvmScarletToolkit/blob/216c0b93361f94f344268fd5f084fbcb4d466086/src/MvvmScarletToolkit.Implementations/ScarletCommandManager.cs#L10

The current implementation relies on CommandManager. The fix is pretty easy, since you already abstracted it away behind an IScarletCommandManager

Something like this COULD do the job(needs re-evaluation by somebody more experienced than me):

        public sealed class UwpScarletCommandManager : IScarletCommandManager
        {
            private static readonly Lazy<UwpScarletCommandManager > _default = new Lazy<ScarletCommandManager>(() => new UwpScarletCommandManager ());

            public static IScarletCommandManager Default { get; } = _default.Value;

            public event EventHandler RequerySuggested { get; set; }

            public void InvalidateRequerySuggested()
            {
                CanExecuteChanged?.Invoke(this, EventArgs.Empty);
            }
        }

This solution is basically from this stackoverflow thread: https://stackoverflow.com/questions/12030697/what-replaces-commandmanager-in-winrt

[Insire]

I've come up with this based on your link and little of my own googling. Gonna test it somewhen and add it to the repo after that.

    public sealed class UwpScarletCommandManager : IScarletCommandManager
    {
        private static readonly Lazy<UwpScarletCommandManager> _default = new Lazy<UwpScarletCommandManager>(() => new UwpScarletCommandManager());

        public static IScarletCommandManager Default { get; } = _default.Value;

        public event EventHandler? RequerySuggested;

        public void InvalidateRequerySuggested()
        {
            RequerySuggested?.Invoke(this, EventArgs.Empty);
        }
    }

[mastorm]

Will test this in my app too, gonna add it here if i notice a rough edge or something