Adding some Sugessstion

As per my view. It is better to expand the navigation bar with the subtopics on the left hand side. when we get to the quick start section. have to scroll down until the end to see what content is here. Therefore, I would like to suggest that it would be better if it could be divided into main subtopics in the nav bar. Therefore, I'd like to suggest that you make it more user-friendly. 

まず、ReactドキュメントWebサイトのQuick Startセクションと現在の左側ナビゲーションを確認します。役立つQuick Startのサブトピックを定義し、ユーザーがセクション全体をスクロールしなくてもナビゲーションからそれらにアクセスできることを確認します。