Look for additional facade aliases in app config array

In my Lumen app, I load my providers and aliases from a `config/app.php` file like in Laravel. Maybe that is uncommon, but this simple PR will include those aliases as well if any are present.

src/Generator.php

@@ -238,6 +238,8 @@ class Generator
           //'Validator' => 'Illuminate\Support\Facades\Validator',
         ];
         
+        $facades = array_merge($facades, $this->config->get('app.aliases', []));
+
         // Only return the ones that actually exist
         return array_filter($facades, function($alias){
             return class_exists($alias);