Update dependency highlight.js to v11

src/lib/angular-material-datetimepicker/index.html

@@ -4,7 +4,7 @@
   <meta http-equiv="content-type" content="text/html; charset=UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <link href="http://fonts.googleapis.com/css?family=Roboto:400,500" rel="stylesheet" type="text/css">
-  <link href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.9.0/styles/github.min.css" rel="stylesheet">
+  <link href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/styles/github.min.css" rel="stylesheet">
   <link href="https://cdnjs.cloudflare.com/ajax/libs/angular-material/1.1.3/angular-material.min.css" rel="stylesheet"
         type="text/css"/>
   <link rel="stylesheet" href="./css/material-datetimepicker.css" type="text/css"/>
@@ -131,7 +131,7 @@ <h2>
 <script type="text/javascript"
         src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment-with-locales.min.js"></script>
 <script type="text/javascript"
-        src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.9.0/highlight.min.js"></script>
+        src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></script>
 <script type="text/javascript" src="./beautifier.js"></script>
 <script type="text/javascript" src="./js/angular-material-datetimepicker.js"></script>
 <script type="text/javascript" src="./js/demo.js"></script>