Fix favicon path

Author: charlescyt

web/index.html

@@ -27,7 +27,7 @@
     <link rel="apple-touch-icon" href="icons/Icon-192.png" />
 
     <!-- Favicon -->
-    <link rel="icon" type="image/png" href="/favicon.png" />
+    <link rel="icon" type="image/png" href="favicon.png" />
 
     <title>Dart AST Node Viewer</title>
     <link rel="manifest" href="manifest.json" />