Run tests on PHP 8.3 and update test suite

[yadaiio]

Builds on top of #30, #35, #36 and #37.

References: reactphp/socket#300, clue/reactphp-zenity#63, clue/reactphp-csv#33 and others.

After this is merged, I also want to create another pull request that fix the typos, improve the documentation. 👍

[SimonFrings]

Looks good so far, I have two suggestions that are currently missing from this PR:

1. Can you also update the comment inside the phpunit.xml.legacy, similar to my changes in ReactPHP CSV
2. We also use these PRs to improve the indentation inside the composer.json, similar to my changes in ReactPHP CSV

[SimonFrings]

It also seems like the tests for HHVM are currently failing, didn't notice while reviewing. Can you look into this?

[yadaiio]

Looks good so far, I have two suggestions that are currently missing from this PR:

1. Can you also update the comment inside the `phpunit.xml.legacy`, similar to [my changes in ReactPHP CSV](https://github.com/clue/reactphp-csv/pull/33/files#diff-90e8ed4d404ab38c64ae8ee57d9df2b954891d9d57054048a77df0a385f3a612L3-R3)

2. We also use these PRs to improve the indentation inside the `composer.json`, similar to [my changes in ReactPHP CSV](https://github.com/clue/reactphp-csv/pull/33/files#diff-d2ab9925cad7eac58e0ff4cc0d251a937ecf49e4b6bf57f8b95aab76648a9d34L23-R30)

Done! Thank you @SimonFrings 👍

[yadaiio]

It also seems like the tests for HHVM are currently failing, didn't notice while reviewing. Can you look into this?

It seems like we give an array in the React/Promise(any) function but HHVM expects an React\Promise\Iterable which doesn't exist. I decided to skip the tests for HHVM as the error message doesn't make much sense and HHVM is outdated anyway. Normally an array is the alias for iterable, see https://www.php.net/manual/en/language.types.iterable.php, so the thrown error message is invalid in my opinion.

Tests are running green now. 👍

[SimonFrings]

Thanks for applying the suggested changes, PR looks good to me 👍

[SimonFrings]

Thanks for applying the changes, looks good to me 👍

[yadaiio]

As today is my last day working with you @clue, we agreed closing this pull request and revisit this later on.

If anyone is needing these changes earlier than expected, please consider sponsoring @clue via https://github.com/sponsors/clue. ❤️