fix: 🩹 properly return engine from if/else

lib/comfpile/core.rb

@@ -61,9 +61,11 @@ module Comfpile
             new_engine = if(engine_class.is_a? Comfpile::ArtefactEngine)
                 engine_class
             else
-                engine_class.new(self,
+                engine = engine_class.new(self,
                     subpriority: @artefact_prio_counter, **options)
                 @artefact_prio_counter += 1
+
+                engine
             end
 
             yield(new_engine) if block_given?