[core] Add snippet to single commands (#358)

Author: hjuarez20

src/Application.php

@@ -703,7 +703,8 @@ public function getData($filterNamespaces = null, $excludeNamespaces = [], $excl
             'init',
             'list',
             'shell',
-            'server'
+            'server',
+            'snippet'
         ];
 
         $languages = $this->container->get('console.configuration_manager')

src/Descriptor/TextDescriptor.php

@@ -272,7 +272,8 @@ protected function describeApplication(Application $application, array $options
                 'init',
                 'list',
                 'shell',
-                'server'
+                'server',
+                'snippet'
             ];
 
             // add commands by namespace