Misleading in section integrating Electron Packager within README.md.

[zhujin917]

Electron Packager has modified the definition of HookFunction by this commit. But the code below is still using the old syntax.

rebuild/README.md

Lines 100 to 121 in 76b4600

	### How can I integrate this into [Electron Packager](https://github.com/electron/packager)?
	electron-rebuild provides a function compatible with the [`afterCopy` hook](https://electron.github.io/packager/main/interfaces/Options.html#afterCopy)
	for Electron Packager. For example:
	```javascript
	import packager from "@electron/packager";
	import { rebuild } from "@electron/rebuild";
	packager({
	// … other options
	afterCopy: [
	(buildPath, electronVersion, platform, arch, callback) => {
	rebuild({ buildPath, electronVersion, arch })
	.then(() => callback())
	.catch((error) => callback(error));
	},
	],
	// … other options
	});
	```

The current definition of HookFunction can be viewed here.

What's more, the domain of the link pointing to "afterCopy hook" is electron.github.io, its documentation is outdated. I can't find the corresponding repository for that website, nor do I know who maintains it. I think the API documentation for Electron Packager and Electron Rebuild is at the domain packages.electronjs.org. 🤔