Update friendsofphp/php-cs-fixer requirement || ^3.0 (#21)

Author: dependabot-preview[bot]

composer.json

@@ -20,7 +20,7 @@
   },
   "require-dev": {
     "phpunit/phpunit": "^5.7 || ^6.5 || ^7.0 || ^8.0",
-    "friendsofphp/php-cs-fixer": "^2.19"
+    "friendsofphp/php-cs-fixer": "^2.19 || ^3.0"
   },
   "autoload": {
     "psr-4": {