fix incorrect image name in readme.dev
fix incorrect image name in readme.dev

byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,byran/cyber-dojo-web,cyber-dojo/web