Explore switching from jest to vitest

[bmish]

Exploring here:

• https://github.com/bmish/eslint-doc-generator/compare/vitest?expand=1

To fix still:

• Need to replace mock-fs in all the tests which isn't well supported anymore: https://kschaul.com/til/2024/06/26/mock-fs-with-vitest-and-memfs/

vitest may have better native support for ESM/TypeScript and potential performance benefits.

I'm also running into issues when trying to upgrade to Jest 30 because of our complex package-json.ts code for loading eslint plugins.

Related:

• test: change test runner to vitest eslint-community/eslint-plugin-eslint-plugin#525