Add static propert MaxNumberOfRetries.

This is necessary so that the DeviceSession instance can get this setting. There is no direct access to the settings in BotBase at the moment.
This property will be set when calling the Start method for the bot and is the same for all bots in the same application.

TelegramBotBase/Sessions/DeviceSession.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
@@ -876,5 +876,15 @@ namespace TelegramBotBase.Sessions
         }
 
         #endregion
+
+        #region "Static"
+
+        /// <summary>
+        /// Indicates the maximum number of times a request that received error 
+        /// 429 will be sent again after a timeout until it receives code 200 or an error code not equal to 429.
+        /// </summary>
+        public static uint MaxNumberOfRetries { get; set; }
+
+        #endregion "Static"
     }
 }