docs: Add note to rewrite example about localePrefix (closes #737)

docs/pages/docs/routing/middleware.mdx

@@ -441,9 +441,9 @@ import createIntlMiddleware from 'next-intl/middleware';
 import {NextRequest} from 'next/server';
 
 export default async function middleware(request: NextRequest) {
-  const [, locale, pathname] = request.nextUrl.pathname.split('/');
+  const [, locale, ...segments] = request.nextUrl.pathname.split('/');
 
-  if (pathname === 'profile') {
+  if (locale != null && segments.join('/') === 'profile') {
     const usesNewProfile =
       (request.cookies.get('NEW_PROFILE')?.value || 'false') === 'true';
 
@@ -465,6 +465,8 @@ export const config = {
 };
 ```
 
+Note that if you use a [`localePrefix`](#locale-prefix) other than `always`, you need to adapt the handling appropriately to handle unprefixed pathnames too.
+
 ### Example: Integrating with Clerk
 
 [`@clerk/nextjs`](https://clerk.com/docs/references/nextjs/overview) provides a middleware that can be integrated with `next-intl` by using the [`beforeAuth` hook](https://clerk.com/docs/references/nextjs/auth-middleware#using-before-auth-to-execute-middleware-before-authentication). By doing this, the middleware from `next-intl` will run first, potentially redirect or rewrite incoming requests, followed by the middleware from `@clerk/next` acting on the response.