feat(app): use logo mark as favicon

index.html

@@ -3,6 +3,7 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <link rel="icon" type="image/png" href="/margin-mark.png" />
     <title>margin</title>
   </head>
   <body>