chore: implement WPGraphQL Coding Standards

[justlevine]

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What does this implement/fix? Explain your changes.

This PR implements the WPGraphQL Coding Standards phpcs ruleset and lints the codebase.

Requires (and includes): #763, #764, #765, #766, #767, #768

The sniffs addressed in this PR are mainly cosmetic, however implementing the ruleset will prevent the issues addressed in the related PRs from leaking back into the codebase. It is implemented separately from the related PRs, as those are good merge candidates regardless of whether WooGraphQL adopts this ruleset.

Does this close any currently open issues?

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Any relevant logs, error output, GraphiQL screenshots, etc?

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Any other comments?

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Where has this been tested?

• WooGraphQL Version: 0.14.1
• WPGraphQL Version: 1.14.6
• WordPress Version: 6.2.2
• WooCommerce Version: 7.8.2

[kidunot89]

@justlevine Excellent work, my dude 👍