Fix not all code paths return a value error

Author: Yehudah Asher[user]

AngleSharp.Io/ConfigurationExtensions.cs

@@ -46,6 +46,8 @@ public static IConfiguration WithHttpRequesters(this IConfiguration configuratio
                 var service = new LoaderService(requesters);
                 return configuration.With(service);
             }
+
+            return configuration;
         }
     }
 }