chore: PHP 8 support (#920)

Author: C0kkie

composer.json

@@ -24,12 +24,12 @@
         }
     ],
     "require": {
-        "php": "^7.3",
+        "php": "^7.3|^8.0",
         "illuminate/support": "^8.0",
         "laracasts/flash": "^3.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.0",
+        "phpunit/phpunit": "^9.0|^9.3.3",
         "mockery/mockery": "^1.3.1"
     },
     "autoload": {