Create engine

[fiedl]

Create a demo engine providing simple test javascript code.

https://guides.rubyonrails.org/engines.html

[fiedl]

[2020-01-26 11:46:12] fiedl@fiedl-mbp ~/rails/webpacker-engine-test master
▶ rails plugin new my_engine --full
      create
      create  README.md
      create  Rakefile
      create  my_engine.gemspec
      create  MIT-LICENSE
      create  .gitignore
      create  Gemfile
      create  app/models
      create  app/models/.keep
      create  app/controllers
      create  app/controllers/.keep
      create  app/mailers
      create  app/mailers/.keep
      create  app/assets/images/my_engine
      create  app/assets/images/my_engine/.keep
      create  app/helpers
      create  app/helpers/.keep
      create  app/views
      create  app/views/.keep
      create  config/routes.rb
      create  lib/my_engine.rb
      create  lib/tasks/my_engine_tasks.rake
      create  lib/my_engine/version.rb
      create  lib/my_engine/engine.rb
      create  app/assets/config/my_engine_manifest.js
      create  app/assets/stylesheets/my_engine
      create  app/assets/stylesheets/my_engine/.keep
      create  bin/rails
      create  test/test_helper.rb
      create  test/my_engine_test.rb
      append  Rakefile
      create  test/integration/navigation_test.rb
  vendor_app  test/dummy