adds region tags for pubsub app

Author: bshaffer

pubsub/app/index.php

@@ -22,8 +22,10 @@
 $app = require_once __DIR__ . '/app.php';
 
 $app['project_id'] = getenv('GOOGLE_PROJECT_ID') ?: getenv('GCLOUD_PROJECT');
+# [START pubsub_variables]
 $app['topic'] = 'php-example-topic';
 $app['subscription'] = 'php-example-subscription';
+# [END pubsub_variables]
 $app['debug'] = true;
 
 $app->run();