fix(docs): fix theme flash script and remove unused public/index.html

- Fix data-theme -> data-tiny-theme in the flash-prevention script
- Delete public/index.html (leftover from CRA, unused by Vite)

Author: wangdicoder

apps/docs/index.html

@@ -16,7 +16,7 @@
         (function() {
             var theme = localStorage.getItem('ty-theme');
             if (theme === 'dark' || theme === 'light') {
-                document.documentElement.setAttribute('data-theme', theme);
+                document.documentElement.setAttribute('data-tiny-theme', theme);
             }
         })();
     </script>