Consolidates the docker image (base vs. action) and adds several rubocop extensions.
- Adds the following rubocop extensions to the docker image:
- rubocop-performance
- rubocop-minitest
- rubocop-rspec
- rubocop-rails
- rubocop-thread_safety
- rubocop-i18n
- rubocop-rake
These extensions can now be required in a .rubocop.yml config and used with the rubocop runner.