deps: add rubocop

Gemfile

@@ -3,3 +3,4 @@ source "https://rubygems.org"
 git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 
 # gem "rails"
+gem 'rubocop', group: 'development', require: false

Gemfile.lock

@@ -1,12 +1,39 @@
 GEM
   remote: https://rubygems.org/
   specs:
+    ast (2.4.2)
+    json (2.7.2)
+    language_server-protocol (3.17.0.3)
+    parallel (1.24.0)
+    parser (3.3.1.0)
+      ast (~> 2.4.1)
+      racc
+    racc (1.7.3)
+    rainbow (3.1.1)
+    regexp_parser (2.9.0)
+    rexml (3.2.6)
+    rubocop (1.63.4)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.3.0.2)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.31.3)
+      parser (>= 3.3.1.0)
+    ruby-progressbar (1.13.0)
+    unicode-display_width (2.5.0)
 
 PLATFORMS
   x64-mingw-ucrt
   x86_64-linux
 
 DEPENDENCIES
+  rubocop
 
 BUNDLED WITH
    2.5.9