Translate Complete(kr) : Action Cable Overview - 1st Modified

[yhk1038]

Summary

Translated to korean for ActionCable Overview based on rails new version 5.2

Other Information

• based repository rorlakr/rails-guides
• based branch 5.2-ko
• a file changed: ~/guide/source/ko/action_cable_overview.md
• original guide: Action Cable Overview - Ruby on Rails Guides v5.2
• Modified by feedback of pull request: #73

[yhk1038]

죄송합니다. 풀리퀘스트의 대상 브랜치 설정이 잘못되었네요. 다시 올리겠습니다.