Fix broken url (docker#5829)

Author: joaofnfernandes

get-started/nav.html

@@ -1,5 +1,5 @@
 <ul class="pagination">
-  <li {% if include.selected=="1"%}class="active"{% endif %}><a href="index">1: Orientation</a></li>
+  <li {% if include.selected=="1"%}class="active"{% endif %}><a href="./">1: Orientation</a></li>
   <li {% if include.selected=="2"%}class="active"{% endif %}><a href="part2">2: Containers</a></li>
   <li {% if include.selected=="3"%}class="active"{% endif %}><a href="part3">3: Services</a></li>
   <li {% if include.selected=="4"%}class="active"{% endif %}><a href="part4">4: Swarms</a></li>