feat: laravel 7 (#3)

Author: atymic

composer.json

@@ -12,11 +12,11 @@
   "homepage": "https://github.com/atymic/laravel-dateinterval-cast",
   "require": {
     "php": "^7.3",
-    "laravel/framework": "7.x-dev"
+    "laravel/framework": "^7.0"
   },
   "require-dev": {
     "phpunit/phpunit": "^9.0",
-    "orchestra/testbench": "5.x-dev",
+    "orchestra/testbench": "^5.0",
     "phpstan/phpstan": "^0.12.9"
   },
   "minimum-stability": "dev",