doc: provide alternative to url.parse() using WHATWG URL

PR-URL: https://github.com/nodejs/node/pull/59736
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/url.md

@@ -1847,7 +1847,15 @@ A `URIError` is thrown if the `auth` property is present but cannot be decoded.
 strings. It is prone to security issues such as [host name spoofing][]
 and incorrect handling of usernames and passwords. Do not use with untrusted
 input. CVEs are not issued for `url.parse()` vulnerabilities. Use the
-[WHATWG URL][] API instead.
+[WHATWG URL][] API instead, for example:
+
+```js
+function getURL(req) {
+  const proto = req.headers['x-forwarded-proto'] || 'https';
+  const host = req.headers['x-forwarded-host'] || req.headers.host || 'example.com';
+  return new URL(req.url || '/', `${proto}://${host}`);
+}
+```
 
 ### `url.resolve(from, to)`