Update README.md

Author: 94noni

README.md

@@ -1,6 +1,9 @@
 WebServerBundle
 ===============
 
+**CAUTION**: this bundle is deprecated since Symfony 4.4. Instead, use the
+[Symfony Local Web Server](https://symfony.com/doc/current/setup/symfony_server.html).
+
 WebServerBundle provides commands for running applications using the PHP
 built-in web server. It simplifies your local development setup because you
 don't have to configure a proper web server such as Apache or Nginx to run your