Add Laravel 8 support

Author: torralbodavid

composer.json

@@ -22,11 +22,11 @@
     ],
     "require": {
         "php": "^7.2",
-        "illuminate/support": "^6.5|^7.0"
+        "illuminate/support": "^6.5|^7.0|^8.0"
     },
     "require-dev": {
-        "orchestra/testbench": "^4.0|^5.0",
-        "phpunit/phpunit": "^8.0"
+        "orchestra/testbench": "^4.0|^5.0|^6.0",
+        "phpunit/phpunit": "^8.0|^9.0"
     },
     "autoload": {
         "psr-4": {