Add package auto-discovering

Author: gregoriohc

README.md

@@ -31,7 +31,7 @@ You can install the package via composer:
 composer require laravel-notification-channels/twilio
 ```
 
-You must install the service provider:
+Add the service provider (only required on Laravel 5.4 or lower):
 
 ```php
 // config/app.php

composer.json

@@ -38,5 +38,12 @@
     },
     "config": {
         "sort-packages": true
+    },
+    "extra": {
+        "laravel": {
+            "providers": [
+                "NotificationChannels\\Twilio\\TwilioProvider"
+            ]
+        }
     }
 }