@shopify/eslint-plugin: Add support for ESLint v9 and flat config

[EvgenyOrekhov]

Overview

ESLint v9 was released 2 months ago: https://eslint.org/blog/2024/04/eslint-v9.0.0-released/

Type

• New feature
• Changes to existing features

Motivation

What inspired this feature request? What problems were you facing,
or what else makes you think this should be included?

Impossible to use @shopify/eslint-plugin with ESLint v9

Labels

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Area

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Scope

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  • Tag it with the Package: <package_name> label.

• Is it related to a new package?

  • Tag it with the New package Label

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Checklist

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[andyw8]

This is important to address, as there is the danger that updating to ESLint v9 can result in checks being silently skipped:

https://github.com/Shopify/vscode-shopify-metrics/pull/614