Replace SquizLabs PHPCodeSniffer with Fork

[JosephLeedy]

PHP_CodeSniffer has been abandoned and forked¹. The Composer dependency should be replaced with "phpcsstandards/php_codesniffer": "^3.0". The documentation should also be updated to link to the new repo.

Footnotes

1. https://github.com/PHPCSStandards/PHP_CodeSniffer/issues/109 ↩

[m2-assistant]

Hi @JosephLeedy. Thank you for your report.
To speed up processing of this issue, make sure that you provided sufficient information.
Add a comment to assign the issue: @magento I am working on this

---

Join Magento Community Engineering Slack and ask your questions in #github channel.

[JosephLeedy]

@magento I am working on this

[m2-assistant]

Hi @JosephLeedy! 👋
Thank you for collaboration. Only members of Community Contributors Team are allowed to be assigned to the issue. Please use @magento add to contributors team command to join Contributors team.

[JosephLeedy]

@magento add to contributors team

[m2-assistant]

Hi @JosephLeedy! 👋
Thank you for joining. Please accept team invitation 👉 here 👈 and add your comment one more time.

[JosephLeedy]

@magento I am working on this

[JosephLeedy]

Withdrawn, per #475 (comment).