Add link to configuration documentation

The link is missing from the fundamentals listing.

Author: dhaaker

page_creation.rst

@@ -240,6 +240,7 @@ Ok, time to finish mastering the fundamentals by reading these articles:
 * :doc:`/routing`
 * :doc:`/controller`
 * :doc:`/templating`
+* :doc:`/configuration`
 
 Then, learn about other important topics like the
 :doc:`service container </service_container>`,