리액트 18에서 ReactDOM.render 함수를 사용하고 npm start를 했는데, 다음과 같은 에러 메시지가 콘솔창이 띄워졌다. Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot How to Upgrade to React 18 – React Blog As we shared in the release post, React 18 introduces fe..