Fix @return tag for Enum.included method

The method returns the result of base.extend(ClassMethods), which
returns the base class, not nil.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: horgh

lib/minfraud/enum.rb

@@ -8,7 +8,7 @@ module Enum
     #
     # @param base [Class] The class including this module.
     #
-    # @return [nil]
+    # @return [Class] The base class.
     def self.included(base)
       base.extend(ClassMethods)
     end