feat: Added new autoregistration process and fixed generators

lib/generators/nexus_cqrs/USAGE

lib/generators/nexus_cqrs/command_generator.rb

lib/generators/nexus_cqrs/query_generator.rb

lib/generators/nexus_cqrs/templates/command_handler.rb

lib/generators/nexus_cqrs/templates/query_handler.rb

...generators/nexus_cqrs/templates/register_cqrs_handlers.rb

lib/nexus_cqrs.rb

lib/nexus_cqrs/base_command.rb

lib/nexus_cqrs/base_command_handler.rb

lib/nexus_cqrs/base_message.rb

lib/nexus_cqrs/base_middleware.rb

lib/nexus_cqrs/base_query.rb

lib/nexus_cqrs/base_query_handler.rb

lib/nexus_cqrs/command_bus.rb

lib/nexus_cqrs/command_executor.rb

lib/nexus_cqrs/helpers.rb

lib/nexus_cqrs/version.rb

spec/lib/base_message_spec.rb

spec/lib/command_bus_spec.rb

spec/lib/command_executor_spec.rb