Support for PHP 8.0 (#79)

* Support for PHP 8.0

As mentioned in #78 there are some errors when installing in a PHP 8 setup.

* Update composer.json

composer.json

@@ -24,15 +24,15 @@
         }
     },
     "require": {
-        "php": "^7.4",
+        "php": "^7.4|^8.0",
         "illuminate/console": "^5.8|^6.0|^7.0|^8.0",
         "illuminate/support": "^5.8|^6.0|^7.0|^8.0",
         "nimbusoft/flysystem-openstack-swift": "^0.3.3"
     },
     "require-dev": {
         "phpunit/phpunit": "^7.0|^8.0|^9.0",
         "mockery/mockery": "^1.3 >= 1.3.1",
-        "friendsofphp/php-cs-fixer": "^2.16.1",
+        "friendsofphp/php-cs-fixer": "^2.18",
         "brainmaestro/composer-git-hooks": "^2.8",
         "league/flysystem-cached-adapter": "^1.0 >= 1.0.2",
         "orchestra/testbench": "^3.8|^4.0|^5.0|^6.0"