Apply suggestions from code review

bin/setup

@@ -1,4 +1,6 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
+
 require 'fileutils'
 
 # path to your application root.

bin/yarn

@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+ # frozen_string_literal: true 
 APP_ROOT = File.expand_path('..', __dir__)
 Dir.chdir(APP_ROOT) do
   exec "yarnpkg", *ARGV

config/puma.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Puma can serve each request in a thread from an internal thread pool.
 # The `threads` method setting takes two numbers: a minimum and maximum.
 # Any libraries that use thread pools should be configured to match