add support for Laravel 6 (#259)

* Update composer.json

* Update composer.json

Author: daveismynamecom

composer.json

@@ -11,7 +11,7 @@
     ],
     "require": {
         "php": ">=7.0",
-        "illuminate/support": "5.5.x|5.6.x|5.7.x|5.8.x",
+        "illuminate/support": "5.5.x|5.6.x|5.7.x|5.8.x|6.x",
         "studio-42/elfinder": "~2.1.10",
         "barryvdh/elfinder-flysystem-driver": "^0.2",
         "league/flysystem": "^1.0",