Document we should probably use React.memo under our Context Provider

It is not immediately obvious that when the component that declares the context provider re-renders, all its descendants will also render, and not just the components that subscribe to the context.

This has been made explicit by @sophiebits on Twitter: https://twitter.com/sophiebits/status/1228942768543686656, and @markerikson on his blog: https://blog.isquaredsoftware.com/2020/05/blogged-answers-a-mostly-complete-guide-to-react-rendering-behavior/#context-updates-and-render-optimizations, but following the right people on twitter should not be a requirement to understand how React is supposed to be used.

While it's true that if one reasons about how React decides to render components (given one has a sufficient understanding of it) this behaviour can be inferred, I still think that an explicit recommendation would help a majority of React users.

Happy to try submitting a PR if needed :)

特定のファイルやテストは指定されていません。react.dev のドキュメントで React Context Provider に関するガイダンスを見つけ、リンクされているレンダリングのリファレンスを確認してください。ドキュメントで子孫の再レンダリングが明確に説明され、React.memo に関する意図された推奨事項が示されていれば完了です。