Fix for NME target

[hoseyjoe]

cant compile currently need to add return types. if you need a project: HaxeUITest.zip

haxe/ui/backend/ScreenImpl.hx:67: lines 67-73 : Field addComponent overrides parent class with different or incomplete type

Fix is to add
return component;

...
public override function addComponent(component:Component) {
        component.scaleX = Toolkit.scaleX;
        component.scaleY = Toolkit.scaleY;
        _topLevelComponents.push(component);
        container.addChild(component);
        onContainerResize(null);
        return component;
    }

    public override function removeComponent(component:Component) {
        _topLevelComponents.remove(component);
        container.removeChild(component);
        return component;
    }
...

[hoseyjoe]

This is working now