JsonSerializable should require ext-json

Author: devnix

composer.json

@@ -19,7 +19,8 @@
     },
     "require": {
         "php": "^7.2|^8.0",
-        "gettext/languages": "^2.3"
+        "gettext/languages": "^2.3",
+        "ext-json": "*"
     },
     "require-dev": {
         "phpunit/phpunit": "^8.0|^9.0",