docs: Directory-relative URL

Author: felipecesr

lessons/index.html

@@ -7,7 +7,7 @@
   {% for page in site.pages %}
   {% if page.title and page.url != "/" %}
   <li>
-    <a href="/{{ page.url }}">{{ page.title }}</a>
+    <a href="{{ page.url }}">{{ page.title }}</a>
   </li>
   {% endif %}
   {% endfor %}