README.md in ika3-0.4.0 vs README.md in ika3-0.4.1

- old
+ new

@@ -1,8 +1,10 @@
 # Ika3
 
 [![CircleCI](https://dl.circleci.com/status-badge/img/gh/YutaGoto/ika3/tree/main.svg?style=svg)](https://dl.circleci.com/status-badge/redirect/gh/YutaGoto/ika3/tree/main)
 
+[![Ruby Style Guide](https://img.shields.io/badge/code_style-rubocop-brightgreen.svg)](https://github.com/rubocop/rubocop)
+
 Weapon data from Splatoon3. This is Unofficial data.
 
 ## Installation
 
 Install the gem and add to the application's Gemfile by executing: