Release 2.4.0

Increase minimum required php version to 7.3
Enable on phpunit 9.0
Enable with php-file-iterator 3.0

Author: calbrecht

box.json

@@ -29,5 +29,5 @@
     ],
     "git-commit": "git-commit",
     "git-version": "git-version",
-    "output": "phpcb-2.3.2.phar"
+    "output": "phpcb-2.4.0.phar"
 }