fix: url prefix for favicon (#174)

Author: MunifTanjim

lib/index-html.js

@@ -16,7 +16,7 @@ function indexHtml (opts) {
     ? opts.theme.favicon.map(favicon => `<link rel="${favicon.rel}" type="${favicon.type}" href="${prefix}/theme/${favicon.filename}" sizes="${favicon.sizes}" />\n`).join('')
     : `
       <link rel="icon" type="image/png" href="${prefix}/favicon-32x32.png" sizes="32x32" />
-      <link rel="icon" type="image/png" href=".${opts.prefix}/favicon-16x16.png" sizes="16x16" />
+      <link rel="icon" type="image/png" href="${prefix}/favicon-16x16.png" sizes="16x16" />
       `}
       </head>