Add Language model and LanguageController

spec/requests/root_spec.rb

@@ -27,6 +27,12 @@ RSpec.describe "Root path", type: :request do
       expect(response.body).to include("Sign Out")
     end
 
+    it "should have the 'Languages' link" do
+      sign_in FactoryBot.create(:user)
+      get root_path
+      expect(response.body).to have_selector(%(a[href="#{languages_path}"]))
+    end
+
     it "should welcome user by username" do
       user = FactoryBot.create(:user)
       sign_in user