Update router.prefetch documentation to include locale option

docs/api-reference/next/router.md

@@ -248,14 +248,16 @@ export default function Page() {
 
 Prefetch pages for faster client-side transitions. This method is only useful for navigations without [`next/link`](/docs/api-reference/next/link.md), as `next/link` takes care of prefetching pages automatically.
 
-> This is a production only feature. Next.js doesn't prefetch pages on development.
+> This is a production only feature. Next.js doesn't prefetch pages in development.
 
 ```jsx
-router.prefetch(url, as)
+router.prefetch(url, as, options)
 ```
 
 - `url` - The URL to prefetch, including explicit routes (e.g. `/dashboard`) and dynamic routes (e.g. `/product/[id]`)
 - `as` - Optional decorator for `url`. Before Next.js 9.5.3 this was used to prefetch dynamic routes, check our [previous docs](https://nextjs.org/docs/tag/v9.5.2/api-reference/next/link#dynamic-routes) to see how it worked
+- `options` - Optional object with the following allowed fields:
+  - `locale` - allows providing a different locale from the active one. If `false`, `url` has to include the locale as the active locale won't be used.
 
 #### Usage