docs: Opting out of scrolling with `next/link` and `useRouter`. (#53804)
Addressing comments from https://github.com/vercel/next.js/issues/49087.
Introduced with https://github.com/vercel/next.js/pull/51869.
Related https://github.com/vercel/next.js/issues/50105.
This PR adds documentation for `next/link` and useRouter` about how to disable scroll restoration.