add web analytics (plausible)

Author: qdequippe

templates/_snippets/head.twig

@@ -28,4 +28,7 @@
 
     {# this is the last, so prism can be overriden here #}
     <link href="{{ asset('assets/style.css') }}" rel="stylesheet" type="text/css" />
+
+    <script defer data-domain="friendsofphp.org" src="http://plausible.dequippe.tech/js/script.outbound-links.js"></script>
+    <script>window.plausible = window.plausible || function() { (window.plausible.q = window.plausible.q || []).push(arguments) }</script>
 </head>