feat(services-container): Add link to environment variables example

Author: esolitos

en/reference/services-container.html

@@ -555,7 +555,8 @@ <h2 id="nodes">nodes</h2>
 
 <h2 id="environment-variables">environment-variables</h2>
 <p>
-Add children elements to <code>nodes</code> for environment variables - see example below.
+Add children elements to <code>nodes</code> for environment variables - see the <a href="#nodes">example below (in the
+  <code>ndoes</code> section)</a>.
 These are set before the services are started on the container node - available for the Container.
 </p>