Merge branch '40-websockets-chat' into 'Development'

.gitlab-ci.yml

app/assets/javascripts/application.js

app/assets/javascripts/room_channel.js

app/assets/javascripts/rooms.js

app/assets/stylesheets/application.scss

app/assets/stylesheets/buttons.scss

app/assets/stylesheets/scaffolds.scss

app/controllers/api/v1/habits_controller.rb

app/controllers/leaderboards_controller.rb

app/controllers/room_messages_controller.rb

app/controllers/rooms_controller.rb

app/models/leaderboard.rb

app/models/room.rb

app/views/leaderboards/show.html.erb

app/views/rooms/_rooms.html.erb

app/views/rooms/show.html.erb

app/views/shared/_header.html.erb

config/initializers/assets.rb

config/locales/en.yml

db/migrate/20210424183928_add_rooms_to_leaderboards.rb