Amend documentation for skipping useEffect

This is a documentation improvement request.

Currently https://reactjs.org/docs/hooks-effect.html#tip-optimizing-performance-by-skipping-effects explains skipping a useEffect based on a state variable by showing the following code:

useEffect(() => {
  document.title = `You clicked ${count} times`;
}, [count]); // Only re-run the effect if count changes

With the following explanation:

In the example above, we pass [count] as the second argument. What does this mean? If the count is 5, and then our component re-renders with count still equal to 5, React will compare [5] from the previous render and [5] from the next render. Because all items in the array are the same (5 === 5), React would skip the effect. That’s our optimization.

However, as the array we're shown only has a single element it, it is ambiguous what "all the items in the array" means. E.g. we cannot tell whether that's intentional phrasing, or just "plain English" that isn't actually tied to any technical precision.

Could this phrasing either be made more explicit, or (ideally) can an extra paragraph be added to explain what happens to an array with more than one element?

(originally filed as from https://github.com/facebook/react/issues/15068)

Issue でリンクされている docs/hooks-effect.html の「Tip: Optimizing Performance by Skipping Effects」セクションから始めてください。[count] 依存配列の説明を確認し、配列に複数の要素がある場合に比較がどのように機能するかを明確にしてください。ドキュメントで複数要素の場合が曖昧さなく明示的に説明されていれば完了です。