Add mediator examples

src/MediatorPattern/AirTrafficControl/Plane.cs

@@ -0,0 +1,25 @@
+using System;
+
+namespace MediatorPattern.AirTrafficControl
+{
+    public class Plane
+    {
+        public string ID { get; private set; }
+        IAirTrafficControlTower controlTower;
+        public Plane(string id, IAirTrafficControlTower controlTower)
+        {
+            this.controlTower = controlTower;
+            ID = id;
+        }
+
+        public void RequestPermissionToLand()
+        {
+            var lane = controlTower.RequestPermissionToLand(this);
+
+            if (lane.IsPresent)
+                Console.WriteLine("Landing");
+            else
+                Console.WriteLine("I will ask again in 5 minutes");
+        }
+    }
+}