Support webonyx/graphql-php 0.13

Author: Jeremiah VALERIE

composer.json

@@ -16,7 +16,7 @@
     },
     "require": {
         "php": ">=5.6",
-        "webonyx/graphql-php": "^0.11.2|^0.12.0"
+        "webonyx/graphql-php": "^0.11.2 || ^0.12.0 || ^0.13.0"
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.14",