Add debug rectangle size rendering, auto-resize containers to fit all children.

Voile/Source/UI/Widgets/Widget.cs

@@ -32,6 +32,7 @@ public abstract class Widget : IElement, IRenderableElement, IInputElement, IRes
     /// </summary>
     /// <param name="renderer"></param>
     public abstract void Render(RenderSystem renderer, Style style);
+
     /// <summary>
     /// Called when this widget receives input.
     /// </summary>
@@ -45,4 +46,10 @@ public abstract class Widget : IElement, IRenderableElement, IInputElement, IRes
             Size = MinimumRect;
         }
     }
+
+    public void DrawSize(RenderSystem renderer)
+    {
+        renderer.SetTransform(Position, Vector2.Zero);
+        renderer.DrawRectangleOutline(new Vector2(Size.Width, Size.Height), Color.Red, 2.0f);
+    }
 }