chore: add google analytic

Author: booxood

index.html

@@ -127,5 +127,14 @@ <h2 class="hero-intro">一个基于 Github Issue 和 Preact 开发的评论插
 
       gitalk.render('gitalk-container')
     </script>
+    <script>
+      (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+      (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+      m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+      })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');
+
+      ga('create', 'UA-49304532-4', 'auto');
+      ga('send', 'pageview');
+    </script>
   </body>
 </html>