docs: polyfill async

mengxiong10 · mengxiong10 · commit 2b61e8703789 · 2020-06-05T10:51:31.000+08:00
diff --git a/example/index.html b/example/index.html
@@ -7,7 +7,7 @@
     <title>Document</title>
     <link rel="stylesheet" href="https://unpkg.com/normalize.css@8.0.1/normalize.css" />
     <link rel="stylesheet" href="https://unpkg.com/vue2-datepicker/index.css" />
-    <script src="https://polyfill.io/v3/polyfill.js?features=Object.assign,Array.from,Promise,fetch&flags=gated"></script>
+    <script async src="https://polyfill.io/v3/polyfill.js?features=Object.assign,Array.from,Promise,fetch&flags=gated"></script>
   </head>
   <body>
     <div id="app"></div>
