Suggestion realization about HTML5Window

original code (It’s invalid):

suggestion:

	public function setResizable(value:Bool):Bool
	{
		this.resizeElement = value;
		if (this.parent.element != null)
		{
			// from `openfl.displat.Stage` constructor
			if (value == true)
			{
				this.parent.element.style.width = '100%';
				this.parent.element.style.height = '100%';
			}
			else
			{
				this.parent.element.style.width = '';
				this.parent.element.style.height = '';
			}
		}
		return value;
	}