Add Laravel 8 support

Author: iv-craig

composer.json

@@ -12,16 +12,16 @@
         }
     ],
     "require": {
-        "php": "^7.2",
-        "illuminate/notifications": "^6.0|^7.0",
-        "illuminate/support": "^6.0|^7.0",
+        "php": "^7.2|^8.0",
+        "illuminate/notifications": "^6.0|^7.0|^8.0",
+        "illuminate/support": "^6.0|^7.0|^8.0",
         "interfax/interfax": "^1.1"
     },
     "require-dev": {
         "mockery/mockery": "^1.0",
         "mpdf/mpdf": "^8.0",
-        "orchestra/testbench": "~4.0|~5.0",
-        "phpunit/phpunit": "^8.0"
+        "orchestra/testbench": "~4.0|~5.0|~6.0",
+        "phpunit/phpunit": "^8.0|^9.3.3"
     },
     "autoload": {
         "psr-4": {