feat(demo): build a static editor preview for GitHub Pages

web/demo.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />
     <title>RawMark Editor Demo</title>
+    <link rel="icon" href="/icon.svg" type="image/svg+xml" />
   </head>
   <body>
     <div id="app"></div>