Follow standardrb code format

.github/workflows/test.yml

@@ -29,4 +29,5 @@ jobs:
         ruby-version: ${{ matrix.ruby_version }}
         bundler-cache: true
 
+    - run: bundle exec rake standard
     - run: bundle exec rake test

README.md

@@ -78,6 +78,17 @@ To run the test, you need [diff-pdf](https://github.com/vslavik/diff-pdf). You c
     > src# bundle install
     > src# bundle exec rake test
 
+### Linting
+
+    $ bundle exec rake standard
+
+Or fix automatically.
+
+    $ bundle exec rake standard:fix
+
+See https://github.com/standardrb/standard for more details.
+
+
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/hidakatsuya/prawn-disable_word_break. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [code of conduct](https://github.com/hidakatsuya/prawn-disable_word_wrap/blob/master/CODE_OF_CONDUCT.md).

prawn-disable_word_break.gemspec

@@ -24,4 +24,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "test-unit", ">= 3.3.5"
   spec.add_development_dependency "test-unit-rr", ">= 1.0.5"
   spec.add_development_dependency "pdf_matcher-testing", ">= 1.0.0"
+  spec.add_development_dependency "standard", ">= 1.31.0"
 end