added rubocop

.github/workflows/ruby.yml

@@ -35,4 +35,4 @@ jobs:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
     - name: Run tests
-      run: bundle exec rake
+      run: bundle exec rubocop

Gemfile

@@ -0,0 +1,6 @@
+source 'https://rubygems.org'
+git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
+ruby '3.1.2'
+
+gem 'rubocop'

Gemfile.lock

@@ -0,0 +1,41 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.4.2)
+    json (2.6.3)
+    language_server-protocol (3.17.0.3)
+    parallel (1.23.0)
+    parser (3.2.2.4)
+      ast (~> 2.4.1)
+      racc
+    racc (1.7.3)
+    rainbow (3.1.1)
+    regexp_parser (2.8.2)
+    rexml (3.2.6)
+    rubocop (1.57.2)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.2.2.4)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.28.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.30.0)
+      parser (>= 3.2.1.0)
+    ruby-progressbar (1.13.0)
+    unicode-display_width (2.5.0)
+
+PLATFORMS
+  arm64-darwin-22
+
+DEPENDENCIES
+  rubocop
+
+RUBY VERSION
+   ruby 3.1.2p20
+
+BUNDLED WITH
+   2.3.26