Fix URL in index.html
<head>
<!-- Note: cache control not reliable through meta. The below redirection may remain cached in browsers. -->
<!-- Alternatively, use JS. Also, consider https://github.com/rust-lang/cargo/issues/739 in the future. -->
- <meta http-equiv="refresh" content="0; url=/doc/gdnative" />
+ <meta http-equiv="refresh" content="0; url=/docs/gdnative" />
</head>
</html>
