Add active_language controller and cookie storage

config/routes.rb

@@ -3,6 +3,9 @@ Rails.application.routes.draw do
   #get 'dictionary/index'
   resources :dictionary, only: [:index, :show, :create]
   resources :words, only: [:index, :show]
+
+  post '/set_active_language', action: :set_active_language, controller: :active_language
+
   namespace :admin do
     resources :languages
   end