Add frozen string literal comment to files.

Add frozen string literal comment to files.

diff --git a/Gemfile b/Gemfile
index 2a5f647..df32188 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 group :development do
   gem 'translations-manager', git: 'https://github.com/discourse/translations-manager.git'
 end
diff --git a/bin/pull_translations.rb b/bin/pull_translations.rb
index 755a227..789ccaa 100755
--- a/bin/pull_translations.rb
+++ b/bin/pull_translations.rb
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 # Usage:
 #   bundle install
diff --git a/plugin.rb b/plugin.rb
index 1dd03c4..275b961 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # name: discourse-checklist
 # about: Add checklist support to Discourse
 # version: 0.4.1
diff --git a/spec/pretty_text_spec.rb b/spec/pretty_text_spec.rb
index 8e7dee0..2eb6309 100644
--- a/spec/pretty_text_spec.rb
+++ b/spec/pretty_text_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe PrettyText do

GitHub sha: 91dad5c5