A SubState that Fades out and closes
Constructor
new (on_complete:Void ‑> Void, time:Float = 0.5, ?sprite:FlxSprite, color:Int = 0xff000000)
Creates a new substate that fades in and closes
* @param on_complete function to call when fade is complete (FlxG.switchState() is a good choice :P)
* @param time the amount of time to fade in
* @param sprite a sprite to show in place of a solid color
* @param color a color to show in place of black