Docs for cacheSignal

[eps1lon]

Preview: https://react-do5kq6ru7-fbopensource.vercel.app/reference/react/cacheSignal

Mostly taken from facebook/react#33557

[github-actions]

Size changes

📦 Next.js Bundle Analysis for react-dev

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One Page Changed Size

The following page changed size from the code in this PR compared to its base branch:

Page	Size (compressed)	First Load
/[[...markdownPath]]	130.48 KB (🟡 +13 B)	241.02 KB

Details

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[rickhanlonii]

This needs to be explained simple enough to fit on one line in desktop. Something like:

`cacheSignal` allows you to know when a `cache()` is cleared.

[eps1lon]

Suggested change

	`cacheSignal()` returns an [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) which aborts when the cache lifetime is done based on the same execution scope as a [`cache()`](/reference/react/cache)ed function
	`cacheSignal` allows you to know when the `cache()` life time is over.

[rickhanlonii]

This example doesn't make sense because you have no idea that the fetch here is using cache().

Can you use something like a DB example, like here?

https://react-do5kq6ru7-fbopensource.vercel.app/reference/react/cache#preload-data

[eps1lon]

You don't need to know if the call is cached or not. Just that it may be cached by cache().