Add container nesting.

Voile/Source/UI/Containers/Container.cs

@@ -1,27 +1,41 @@
 using System.Numerics;
-using Voile.UI.Widgets;
 
 namespace Voile.UI.Containers;
 
 /// <summary>
-/// A base class for all UI containers, used to position and rendering child <see cref="Widget">s.
+/// A base class for all UI containers, used to position and rendering child <see cref="IElement">s.
 /// </summary>
-public abstract class Container : IElement, IParentableElement
+public abstract class Container : IElement, IParentableElement, IUpdatableElement
 {
     public IReadOnlyList<IElement> Children => _children;
     public Vector2 Position { get; set; }
 
+    public Container()
+    {
+
+    }
+
     public Container(List<IElement> children)
     {
         _children = children;
     }
 
+    public void Update()
+    {
+        Arrange();
+        foreach (var child in _children)
+        {
+            if (child is not IUpdatableElement updatable) continue;
+            updatable.Update();
+        }
+    }
     public abstract void Arrange();
 
     public void AddChild(IElement child)
     {
         _children.Add(child);
+        Update();
     }
 
-    private List<IElement> _children;
+    private List<IElement> _children = new();
 }