Allow version 2.x for xdebug-handler dependency (#69)

Author: mrtnmtth

composer.json

@@ -18,7 +18,7 @@
   },
 
   "require-dev": {
-    "composer/xdebug-handler": "^1.4",
+    "composer/xdebug-handler": "^1.4 || ^2.0",
     "phpunit/phpunit": "^4.8.36 || ^7.5.15"
   },