add google analytics

index.html

@@ -223,5 +223,15 @@ var server = https.createServer({
     <script src="./js/pkijs.org/v1.3.33/x509_simpl.js"></script>
     <script src="./js/browser-csr/v1.0.0-alpha/csr.js"></script>
 
+    <!-- Global site tag (gtag.js) - Google Analytics -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=UA-118745161-2"></script>
+    <script>
+      window.dataLayer = window.dataLayer || [];
+      function gtag(){dataLayer.push(arguments);}
+      gtag('js', new Date());
+
+      gtag('config', 'UA-118745161-2');
+    </script>
+
   </body>
 </html>