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 ↩

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[JosephLeedy]

@magento I am working on this

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[JosephLeedy]

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[JosephLeedy]

@magento I am working on this