Update .gitignore to add coreos directory
Update .gitignore to add coreos directory

dlanileonardo/step-pretty-slack-notify,wantedly/step-pretty-slack-notify,wantedly/step-pretty-slack-notify,dlanileonardo/step-pretty-slack-notify,dlanileonardo/step-pretty-slack-notify,wantedly/step-pretty-slack-notify