Add Mediator pattern description

src/MediatorPattern/MediatorPatternExamples.cs

@@ -32,7 +32,7 @@ namespace MediatorPattern
             //GUI libraries
             //https://www.javacodegeeks.com/2015/09/mediator-design-pattern.html
             //Dispatcher from facebook -> flux -> https://youtu.be/nYkdrAPrdcw?list=PLb0IAmt7-GS188xDYE-u1ShQmFFGbrk0v&t=735
-            // It's almost pub/sub, pub sub is implemented using design pattern, but a mediator assumes more
+            // It's almost pub/sub, pub sub is implemented using mediator design pattern, but a mediator assumes more knowledge of the colleagues
 
         }
 

src/MediatorPattern/StockExchange/StockExchange.cs

@@ -5,6 +5,9 @@ using System.Threading.Tasks;
 
 namespace MediatorPattern.StockExchange
 {
+    /// <summary>
+    /// Mediator implementation
+    /// </summary>
     public class StockExchange : IStockExchange
     {
         Dictionary<string, List<Trader>> sellers;