Add support for Laravel 11

[mfn]

While trying to add Laravel 11 to graphql-laravel, I ran into this package missing support for it as a first.

Summary

• Added automated tests
• Documented for all relevant versions
• Updated the changelog

Changes

• Laravel 11 requires phpunit 10
  • phpunit 10 throws a warning for non-static dataproviders
    Fixing them wasn't as straightforward, as they're calling non-static methods also into the framework; therefore I left this for now as it's only warning (needs to be fixed for phpunit 11)
  • phpstan complained for the same reason, that's why I added them to ignore for now
• orchestra/testbench has no 9.x release yet, so I left in for the final release and added 9.x-dev, to be removed once its out
• Also run tests against PHP 8.3

php-cs-fixer

This one deserves special mention.

I didn't touch anything when it pushed this change onto the PR at first:

-public function __construct(string $message, \Throwable $previous = null, int $code = 0, array $headers = [])
+public function __construct(string $message, ?\Throwable $previous = null, int $code = 0, array $headers = [])

That's when I realized it applies code changes based on the PHP version it runs; but this package supports PHP 7.2+, that's why after that I changed it's runtime.

It still pushed a change, but one which is not an issue with PHP version or compat problems.

Breaking changes

none

[spawnia]

Thank you, nicely done.