Add MarginContainer, mark parent elements dirty when child gets marked dirty too.

Voile/Source/UI/Containers/Container.cs

@@ -60,6 +60,18 @@ public abstract class Container : UIElement, IParentableElement
         }
     }
 
+    public override void MarkDirty()
+    {
+        base.MarkDirty();
+
+        foreach (var child in _children)
+        {
+            if (child is not IUpdatableElement updatable) continue;
+
+            updatable.MarkDirty();
+        }
+    }
+
     /// <summary>
     /// Called when this <see cref="Container"/> has to rearrange its children.
     /// </summary>