Update navbar.html

pages/_includes/parts/navbar.html

@@ -98,7 +98,7 @@
       {% endif %}
 
       <li class="nav-item d-none d-lg-flex mr-3">
-         <a href="https://github.com/tabler/tabler" class="btn btn-sm btn-outline-primary" target="_blank">Source code</a>
+         <a href="{{ site.github_url }}" class="btn btn-sm btn-outline-primary" target="_blank">Source code</a>
       </li>
 
       {% if include.user-menu %}