add favicon on home page

customize.dist/index.html

@@ -4,6 +4,7 @@
     <title>Cryptpad :: Zero Knowledge, Collaborative Real Time Editing</title>
     <meta content="text/html; charset=utf-8" http-equiv="content-type"/>
     <link rel="stylesheet" type="text/css" href="customize/main.css" />
+    <link rel="icon" type="image/png" href="/customize/favicon.png" id="favicon"/>
     <script data-main="/customize/main" src="/bower_components/requirejs/require.js"></script>
     <script src="/bower_components/requirejs/require.js"></script>
     <!-- Piwik -->