Require unreleased version of PHP-CSS-Parser

[pierlon]

Summary

This PR updates the version of PHP-CSS-Parser to the commit MyIntervals/PHP-CSS-Parser@134f4e6, instead of the latest release version 8.3.0. The commit aforementioned includes a fix that would resolve #4197.

A patch is also included for PHP-CSS-Parser to fix the validation of selectors, namely adding ,, \ and @ as valid characters.

Also, I've used the undocumented flag no-api to instruct Composer to retrieve the repository via Git instead of using the GitHub API, due to a rate limit on their API that usually occurs when composer update is run. The alternative to not using no-api is giving Composer your GitHub credentials or creating a GitHub OAuth token, as described here.

Fixes #4197.

Checklist

• My pull request is addressing an open issue (please create one otherwise).
• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[westonruter]

Could you include a test for what is being fixed?

[pierlon]

Done!

[westonruter]

Looks good to me but @schlessera would probably have more to add.