feat: Add favicon (#450)

index.html

@@ -8,6 +8,7 @@
   <meta name="description" content="Description">
   <meta name="viewport"
     content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
+  <link rel="icon" type="image/png" href="images/favicon.png">
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/docsify-themeable@0/dist/css/theme-simple.css">
 </head>
 
@@ -23,4 +24,4 @@
   <script src="//cdn.jsdelivr.net/npm/docsify/lib/docsify.min.js"></script>
 </body>
 
-</html>
+</html>