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)

Inizia con la sezione “Tip: Optimizing Performance by Skipping Effects” di docs/hooks-effect.html, collegata nell’issue. Esamina la spiegazione dell’array delle dipendenze [count] e chiarisci come funzionano i confronti quando un array contiene più elementi. Il lavoro è completato quando la documentazione spiega esplicitamente e senza ambiguità il caso con più elementi.