Update Slim Framework example README

Author: bshaffer

appengine/php72/slim-framework/README.md

@@ -1,7 +1,8 @@
 # Slim Example for App Engine for PHP 7.2
 
 This sample demonstrates how to deploy a *very* basic [Slim][slim] application to
-[Google App Engine for PHP 7.2][appengine-php].
+[Google App Engine for PHP 7.2][appengine-php]. For a more complete guide, follow
+the [getting started](../getting-started) tutorial.
 
 ## Setup
 
@@ -38,4 +39,4 @@ for PHP 7.2 require use of a [front controller][front-controller] file.
 [console]: https://console.developers.google.com/project
 [slim]: https://www.slimframework.com/
 [appengine-php]: https://cloud.google.com/appengine/docs/standard/php/
-[front-controller]: https://stackoverflow.com/questions/6890200/what-is-a-front-controller-and-how-is-it-implemented-in-php
+[front-controller]: https://stackoverflow.com/questions/6890200/what-is-a-front-controller-and-how-is-it-implemented-in-php