Change
lib/generators/supportator/supportator_generator.rb
to
lib/generators/supportator/initializer_generator.rb
Your class name is InitializerGenerator
so file name should be initializer_generator.rb
.
Otherwise, rails would not be able to find it.
In your case with rails g supportator:initializer
, rails would look for a generator file initializer_generator.rb
in lib/generators/supportator
directory.