fix: link for chapter

templates/html/course_index.html

@@ -2,7 +2,7 @@
 <p>{{ abstract }}</p>
 <div class="chapter-toc d-grid gap-2">
     {% for chapter in book %}
-        <a class="btn btn-outline-primary btn-labeled" href="{{ chapter["ident"] }}.html">
+        <a class="btn btn-outline-primary btn-labeled" href="{{ edition }}_chapter_{{ chapter["ident"] }}.html">
             <span class="btn-label">{{loop.index}}</span>{{ chapter["title"]}}
         </a>
     {% endfor %}