composer: add support for Laravel 6.0

Author: mfn

composer.json

@@ -34,8 +34,8 @@
     "type": "project",
     "require": {
         "php": ">= 7.1",
-        "illuminate/contracts": "5.5.*|5.6.*|5.7.*|5.8.*",
-        "illuminate/support": "5.5.*|5.6.*|5.7.*|5.8.*",
+        "illuminate/contracts": "5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
+        "illuminate/support": "5.5.*|5.6.*|5.7.*|5.8.*|^6.0",
         "webonyx/graphql-php": "^0.13",
         "ext-json": "*"
     },