feat(eslint-plugin): support FlatConfig

[naorpeled]

Overview

What is it?

• [ ] Feature / enhancement
• [ ] Bug
• [ x ] Docs / tests / types / typos

Description

Use cases and why

Addresses #6048

• 1. One use case
• 2. Another use case

Checklist:

• [ ] My code follows the developer guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] Added new tests to cover the fix / functionality