Add code examples, and documentation

patterns/memento/MementoPattern/Caretaker.cs

@@ -0,0 +1,24 @@
+namespace MementoPattern;
+
+public class Caretaker
+{
+   //container that could hold memento of Originator
+   //object
+   private readonly Stack<IMemento> _mementos = new();
+   private readonly IOriginator _originator;
+
+   public Caretaker(IOriginator originator)
+   {
+      _originator = originator;
+   }
+
+   public void Save()
+   {
+      _mementos.Push(_originator.GetMemento());
+   }
+
+   public void Undo()
+   {
+      _originator.SetMemento(_mementos.Pop());
+   }
+}