feat: allow PHPUnit 10-12

Author: Chris8934

composer.json

@@ -16,7 +16,7 @@
     ],
     "require": {
         "php": "^7.4 || ^8.0",
-        "phpunit/phpunit": "^9.6.17 || ^10.0 || ^11.0",
+        "phpunit/phpunit": "^9.6.17 || ^10.0 || ^11.0 || ^12.0",
         "php-http/message": "^1.0 || ^2.0",
         "php-http/message-factory": "^1.0",
         "guzzlehttp/psr7": "^1.9 || ^2.0",