Support for ESLint 9 and flat config

[philsherry]

👋 Do you have any plans for updating eslint-watch to support ESLint 9 and its flat config file?

• https://github.com/eslint/eslint/issues/18093
• https://github.com/eslint/eslint/issues/18391

[mreinstein]

This is blocking updating my project to eslint 9, because i'm relying on eslint-watch which is still pegged to eslint <= 8.x