Added support for Dusk 6.0

Author: chinleung

composer.json

@@ -24,7 +24,7 @@
         "browserstack/browserstack-local": "^1.1",
         "guzzlehttp/guzzle": "^6.5|^7.0",
         "illuminate/support": "~5.8.0|^6.0|^7.0|^8.0",
-        "laravel/dusk": "^5.9"
+        "laravel/dusk": "^5.9|^6.0"
     },
     "require-dev": {
         "orchestra/testbench": "3.8.*",