Fixed RunMode.Sync running Async. Added ThrowOnError option.

src/Discord.Net.Commands/CommandServiceConfig.cs

@@ -11,5 +11,11 @@
 
         /// <summary> Gets or sets the minimum log level severity that will be sent to the Log event. </summary>
         public LogSeverity LogLevel { get; set; } = LogSeverity.Info;
+
+        /// <summary> 
+        /// Gets or sets whether RunMode.Sync commands should push exceptions up to the caller. 
+        /// If false or an RunMode.Async command, exceptions are only reported in the Log event. 
+        ///</summary>
+        public bool ThrowOnError { get; set; } = true;
     }
 }