Add Cypress testing workflow initialiser

[X] Add a generator to create a GitHub workflow for Cypress.
[X] Add a generator to add Cypress (via cypress-rails) to a Rails app.
[ ] Add config/initializers/cypress_rails.rb initialiser.
[ ] Add end to end test badge (depends on HealthDataInsight/way_of_working#36)
[ ] At the end of initialisation, run bundle install and bundle exec rake cypress:init (if Rails app w. Gemfile)
[ ] .gitignore needs to include node_modules/ if not already included.

HealthDataInsight / way_of_working-for-hdi