add union type for PHP 8
add union type for PHP 8

apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema,apioo/psx-schema