API renames, change ref renderer to in renderer in IDrawable, make Layer implement IDrawable.

Source/Entities/CircleShape2d.cs

@@ -9,7 +9,7 @@ namespace DaggerFramework
         public float Radius { get => _radius; set => _radius = value; }
         public Color Color { get => _color; set => _color = value; }
 
-        public override void OnDraw(ref Renderer renderer)
+        public override void OnDraw(in Renderer renderer)
         {
             renderer.DrawCircle(_radius, _color);
         }