Added missing SetApiCredentials on socket client

CryptoExchange.Net/Interfaces/ISocketClient.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Threading.Tasks;
+using CryptoExchange.Net.Authentication;
 using CryptoExchange.Net.Objects;
 using CryptoExchange.Net.Sockets;
 
@@ -15,6 +16,12 @@ namespace CryptoExchange.Net.Interfaces
         /// </summary>
         BaseSocketClientOptions ClientOptions { get; }
 
+        /// <summary>
+        /// Set the API credentials for this client. All Api clients in this client will use the new credentials, regardless of earlier set options.
+        /// </summary>
+        /// <param name="credentials">The credentials to set</param>
+        void SetApiCredentials(ApiCredentials credentials);
+
         /// <summary>
         /// Incoming kilobytes per second of data
         /// </summary>