Add pagy test in Contributing guidelines

Author: Paulo Mateus Moura da Silva

CONTRIBUTING.md

@@ -3,6 +3,6 @@
 1. Fork it
 2. Create your feature branch (`git checkout -b my-new-feature`)
 3. Commit your changes and tests (`git commit -am 'Add some feature'`)
-4. Run the tests (`PAGINATOR=kaminari bundle exec rspec; PAGINATOR=will_paginate bundle exec rspec`)
+4. Run the tests (`PAGINATOR=pagy bundle exec rspec; PAGINATOR=kaminari bundle exec rspec; PAGINATOR=will_paginate bundle exec rspec`)
 5. Push to the branch (`git push origin my-new-feature`)
 6. Create a new Pull Request