Update to generate eslint 9.0 plugins

[justinfagnani]

I'm just getting started with eslint plugins, so I'm not sure how big of a deal or necessary this is, but the generator currently generates a project that uses eslint 8.19.

[nzakas]

Plugins will generally work as-is in ESLint v9.0. Please take a look at this page and see if there's anything you're doing that this package isn't providing:
https://eslint.org/docs/latest/extend/plugin-migration-flat-config