ESLint 9

[hnrq]

Description

This PR aims to update the plugin dependencies and stack in order to introduce ESLint 9 Flat Config.

Fixes #166

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

No new features were added. Existing tests are passing

Checklist: (Feel free to delete this section upon completion)

• I have included a changeset if this change will require a version change to one of the packages.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have run all builds, tests, and linting and all checks pass
• I have added tests that prove my fix is effective or that my feature works
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[jonocairns]

@carbonrobot I'd be very appreciative if you could take a look at this ❤️

[Copilot]

Pull Request Overview

This PR updates the ESLint plugin to support ESLint 9 and introduces flat config support while modernizing the codebase from Flow to TypeScript. The changes include migrating from CommonJS to ES modules, updating dependencies, and removing Flow type checking in favor of TypeScript.

• Migrates from Flow to TypeScript for type safety
• Adds ESLint 9 flat config support alongside existing configuration format
• Modernizes the build system from Babel to TypeScript compiler

Reviewed Changes

Copilot reviewed 62 out of 66 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
package.json	Updates dependencies, changes build system from Babel to TypeScript, adds flat config exports
src/flat.ts	New flat config export for ESLint 9 compatibility
src/index.ts	Converts to ES modules and TypeScript, updates rule imports
src/rules/*.ts	Converts all rules from Flow to TypeScript with updated type definitions
tests/*.test.ts	Updates test files to use new language options mapper for ESLint 9
config files	Replaces ESLint legacy config with flat config, removes Babel/Flow configuration

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