fix headwayapp link

EryouHao · EryouHao · commit 6a3c15bb0adc · 2019-12-19T19:17:18.000+08:00
diff --git a/public/index.html b/public/index.html
@@ -236,7 +236,7 @@
     <script defer src="https://cdn.jsdelivr.net/npm/katex@0.10.2/dist/katex.min.js" integrity="sha384-9Nhn55MVVN0/4OFx7EE5kpFBPsEMZxKTCnA+4fqDmg12eCTqGi6+BB2LjY8brQxJ" crossorigin="anonymous"></script>
     <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Droid+Serif:400,700">
     <link href="https://cdn.remixicon.com/releases/v2.1.0/remixicon.css" rel="stylesheet">
-    <script src="//cdn.headwayapp.co/widget.js"></script>
+    <script src="https://cdn.headwayapp.co/widget.js"></script>
   </head>
   <body>
     <noscript>
