Typed properties requires PHP 7.4

[kedodrill]

Hi there, I tried to install this but received an error about the UrlGenerator type in https://github.com/mll-lab/laravel-graphiql/blob/master/src/GraphiQLController.php

I'm on PHP 7.2.14, and typed properties aren't available until 7.4; however, the PHP version in composer.json for this project states that ^7.1 || ^8, so I'm able to install it. Installing 1.2.2 works fine.