Allow laravel 9.0

Author: Bram Ceulemans

composer.json

@@ -18,7 +18,7 @@
     ],
     "require": {
         "php": "^7.4|^8.0",
-        "illuminate/contracts": "^8.0"
+        "illuminate/contracts": "^8.0|^9.0"
     },
     "require-dev": {
         "brianium/paratest": "^6.3",
@@ -46,7 +46,10 @@
         "test-coverage": "vendor/bin/phpunit --coverage-html coverage"
     },
     "config": {
-        "sort-packages": true
+        "sort-packages": true,
+        "allow-plugins": {
+            "phpstan/extension-installer": true
+        }
     },
     "extra": {
         "branch-alias": {