List supported drives in cache and broadcasting configs

config/broadcasting.php

@@ -11,6 +11,8 @@ return [
     | framework when an event needs to be broadcast. You may set this to
     | any of the connections defined in the "connections" array below.
     |
+    | Supported: "pusher", "redis", "log"
+    |
     */
 
     'default' => env('BROADCAST_DRIVER', 'pusher'),

config/cache.php

@@ -11,6 +11,8 @@ return [
     | using this caching library. This connection is used when another is
     | not explicitly specified when executing a given caching function.
     |
+    | Supported: "apc", "array", "database", "file", "memcached", "redis"
+    |
     */
 
     'default' => env('CACHE_DRIVER', 'file'),