Added AddOcelot Configbuilder Overload

Added an AddOcelot overload to load FileConfiguration directly from the application, so that all the routes could be made configurable and could be load from anywhere.

src/Ocelot/DependencyInjection/ConfigurationBuilderExtensions.cs

@@ -81,5 +81,20 @@ public static IConfigurationBuilder AddOcelot(this IConfigurationBuilder builder
 
             return builder;
         }
+
+
+        public static IConfigurationBuilder AddOcelot(
+            this IConfigurationBuilder builder, FileConfiguration fileConfiguration, IWebHostEnvironment env)
+        {
+            const string primaryConfigFile = "ocelot.json";
+
+            var json = JsonConvert.SerializeObject(fileConfiguration);
+
+            File.WriteAllText(primaryConfigFile, json);
+
+            builder.AddJsonFile(primaryConfigFile, false, false);
+
+            return builder;
+        }
     }
 }