Add xml ext. to requirements list in README

1 job from master in 4 minutes and 33 seconds (queued for 4 minutes and 7 seconds)
Status Job ID Name Coverage
  Test
failed #52001289
test

00:04:33

 
Name Stage Failure
failed
test Test
  <meta property="og:type" content="website">
<meta property="og:url" content="http://localhost/">
<meta property="og:image" content="http://localhost/apple-touch-icon-precomposed.png">

<link rel="alternate" type="application/atom+xml" href="/featured/hot/1.atom" title="
Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 32768 bytes) in /builds/jorgesumle/raddit-app/var/cache/test/translations/catalogue.en.52lf549.php on line 1

Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 32768 bytes) in /builds/jorgesumle/raddit-app/var/cache/test/ContainerErD8zU7/getSwiftmailer_EmailSender_ListenerService.php on line 1
ERROR: Job failed: exit code 1