Add frozen_string_literal magic comment

re: https://www.rubydoc.info/gems/rubocop/RuboCop/Cop/Style/FrozenStringLiteralComment

spec/support/api_schema_matcher.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Source: https://robots.thoughtbot.com/validating-json-schemas-with-an-rspec-matcher
 
 RSpec::Matchers.define :match_response_schema do |schema|

spec/support/database_cleaner.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 RSpec.configure do |config|
   config.before(:suite) do
     DatabaseCleaner.clean_with(:truncation)

spec/support/external_request.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Mock external requests to youtube
 require 'webmock/rspec'
 WebMock.disable_net_connect!(allow_localhost: true, allow: /stripe.com/)

spec/support/factory_girl.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative 'external_request'
 
 RSpec.configure do |config|

spec/support/flash.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Flash
   def flash
     results = all(:css, 'div#flash p')

spec/support/kneet_connections.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   class Base
     mattr_accessor :shared_connection

spec/support/login_macros.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module LoginMacros
   include Warden::Test::Helpers
   Warden.test_mode!

spec/support/omniauth_macros.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module OmniauthMacros
   # The mock_auth configuration allows you to set per-provider (or default)
   # authentication hashes to return during integration testing.

spec/support/save_feature_failures.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Automatically save the page a test fails
 Capybara.save_and_open_page_path = Rails.root.join('tmp', 'capybara')
 

spec/support/sidebar.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Sidebar
   def sidebar
     @conference = create(:conference)