Update README.md

It took me many hours to debug the problem with http events. Pusher sending requests as http instead of https using cURL which was causing the problem, and I solved it by adding scheme to options .

Author: zeyad82

README.md

@@ -159,6 +159,7 @@ The HTTP subscriber is compatible with the Laravel Pusher subscriber. Just confi
     'options' => [
         'host' => 'localhost',
         'port' => 6001,
+        'scheme' => 'http'
     ],
 ],
 ```