Temporary fix to go to book index

Author: Songtech-0912

templates/page.html

@@ -39,7 +39,7 @@ <h1>{{ page.title }}</h2>
         <!-- jump to TOC button -->
         {% if not page.extra.notoc %}
         <a id="jump-toc-btn" href="#toc">Show table of contents</a>
-        <a href="/" class="return-link">Back to home</a>
+        <a href="../" class="return-link">Back to index</a>
         {% endif %}
     </article>