Use frozen string literal in root files

.rubocop.yml

@@ -83,20 +83,8 @@ Style/FrozenStringLiteralComment:
   Enabled: true
   EnforcedStyle: always
   Include:
-    - 'activesupport/**/*'
-    - 'activemodel/**/*'
-    - 'actioncable/**/*'
-    - 'activejob/**/*'
-    - 'activerecord/**/*'
-    - 'activestorage/**/*'
-    - 'actionmailer/**/*'
-    - 'actionview/**/*'
-    - 'actionpack/**/*'
-    - 'ci/**/*'
-    - 'guides/**/*'
-    - 'tasks/**/*'
-    - 'tools/**/*'
   Exclude:
+    - 'railties/**/*'
     - 'actionview/test/**/*.builder'
     - 'actionview/test/**/*.ruby'
     - 'actionpack/test/**/*.builder'

Gemfile

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source "https://rubygems.org"
 
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }

Rakefile

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "net/http"
 
 $:.unshift __dir__

rails.gemspec

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 version = File.read(File.expand_path("RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|

version.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Rails
   # Returns the version of the currently loaded Rails as a <tt>Gem::Version</tt>
   def self.gem_version