Fix Rubocop linter errors

feat/setup

Gemfile

@@ -1,11 +1,11 @@
-source "https://rubygems.org"
+source 'https://rubygems.org'
 
 # Bundle edge Rails instead: gem "rails", github: "rails/rails", branch: "main"
-gem "rails", "~> 7.2.1", ">= 7.2.1.2"
+gem 'rails', '~> 7.2.1', '>= 7.2.1.2'
 # Use postgresql as the database for Active Record
-gem "pg", "~> 1.1"
+gem 'pg', '~> 1.1'
 # Use the Puma web server [https://github.com/puma/puma]
-gem "puma", ">= 5.0"
+gem 'puma', '>= 5.0'
 # Build JSON APIs with ease [https://github.com/rails/jbuilder]
 # gem "jbuilder"
 # Use Redis adapter to run Action Cable in production
@@ -18,10 +18,10 @@ gem "puma", ">= 5.0"
 # gem "bcrypt", "~> 3.1.7"
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
-gem "tzinfo-data", platforms: %i[ windows jruby ]
+gem 'tzinfo-data', platforms: %i[windows jruby]
 
 # Reduces boot times through caching; required in config/boot.rb
-gem "bootsnap", require: false
+gem 'bootsnap', require: false
 
 # Use Active Storage variants [https://guides.rubyonrails.org/active_storage_overview.html#transforming-images]
 # gem "image_processing", "~> 1.2"
@@ -31,14 +31,13 @@ gem "bootsnap", require: false
 
 group :development, :test do
   # See https://guides.rubyonrails.org/debugging_rails_applications.html#debugging-with-the-debug-gem
-  gem "debug", platforms: %i[ mri windows ], require: "debug/prelude"
+  gem 'debug', platforms: %i[mri windows], require: 'debug/prelude'
 
   # Static analysis for security vulnerabilities [https://brakemanscanner.org/]
-  gem "brakeman", require: false
+  gem 'brakeman', require: false
 
   # Omakase Ruby styling [https://github.com/rails/rubocop-rails-omakase/]
-  gem "rubocop-rails-omakase", require: false
+  gem 'rubocop-rails-omakase', require: false
 end
 
 gem 'rubocop', '>= 1.0', '< 2.0'
-

app/mailers/application_mailer.rb

@@ -1,4 +1,4 @@
 class ApplicationMailer < ActionMailer::Base
-  default from: "from@example.com"
-  layout "mailer"
+  default from: 'from@example.com'
+  layout 'mailer'
 end

config.ru

@@ -1,6 +1,6 @@
 # This file is used by Rack-based servers to start the application.
 
-require_relative "config/environment"
+require_relative 'config/environment'
 
 run Rails.application
 Rails.application.load_server