Add documentation to IElement, Anchor and UIElement.

Voile/Source/UI/UIElement.cs

@@ -3,6 +3,9 @@ using Voile.Rendering;
 
 namespace Voile.UI;
 
+/// <summary>
+/// Base class for all UI elements. 
+/// </summary>
 public abstract class UIElement : IElement, IRenderableElement, IResizeableElement, IUpdatableElement, IAnchorableElement
 {
     public bool Visible { get; set; } = true;
@@ -43,6 +46,10 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
 
     public virtual void MarkDirty() => _dirty = true;
 
+    /// <summary>
+    /// Sets a parent element for this <see cref="UIElement"/>.
+    /// </summary>
+    /// <param name="parent">Element to parent this <see cref="UIElement"/> to.</param>
     public void SetParent(UIElement parent)
     {
         _parent = parent;