Add support for eager-loading kpop

* On the Kpop::Engine we have set `config.eager_load_namespaces << Katalyst::Kpop` which requires `Katalyst::Kpop` module to include `eager_load!` method, provided by extending `ActiveSupport::Autoload`

Author: hasarindaKI

lib/katalyst/kpop.rb

@@ -8,5 +8,6 @@
 
 module Katalyst
   module Kpop
+    extend ActiveSupport::Autoload
   end
 end