feat: laravel 8 support (#4)

Author: atymic

README.md

@@ -8,7 +8,7 @@
 Laravel has built-in casting for `date` & `datetime` types, but if you want to use ISO 8061 durations with the native
 `DateInterval` class, or Carbon's `CarbonInterval` you're out of luck.
 
-This package provides two custom casts (for `DateInterval` and `CarbonInterval` respectively) using Laravel 7.x's custom
+This package provides two custom casts (for `DateInterval` and `CarbonInterval` respectively) using Laravel 7.x/8.x's custom
 casts feature.
 
 ## Installation

composer.json

@@ -12,11 +12,11 @@
   "homepage": "https://github.com/atymic/laravel-dateinterval-cast",
   "require": {
     "php": "^7.3",
-    "laravel/framework": "^7.0"
+    "laravel/framework": "^7.0 || ^8.0"
   },
   "require-dev": {
     "phpunit/phpunit": "^9.0",
-    "orchestra/testbench": "^5.0",
+    "orchestra/testbench": "^5.0 || ^6.0",
     "phpstan/phpstan": "^0.12.9"
   },
   "minimum-stability": "dev",