Update service_container/factories.rst

Author: OskarStark

service_container/factories.rst

@@ -99,6 +99,8 @@ create its object:
     only depends on the object that is returned by the factory. However,
     the configured class name may be used by compiler passes and therefore
     should be set to a sensible value.
+Using the Class as Factory Itself
+---------------------------------
 
 When the static factory method is on the same class as the created instance, the class name can be omitted from the factory declaration.
 of the class itself.