Update index.html

Author: m0ver

index.html

@@ -51,7 +51,7 @@
                 </a>
             </li>
             <li class="nav-item">
-                <a href="en/api/README.html" class="nav-link">
+                <a href="en/api/" class="nav-link">
                     <ion-icon name="code-slash-outline"></ion-icon>
                     <span>API Reference</span>
                 </a>