Mark vitest as an optional peer dependency with peerDependenciesMeta

[ericmatthys]

Similar to the reasoning in jest-community/eslint-plugin-jest#970, a shareable ESLint config does not need to depend directly on vitest. For example, in a monorepo it's common to have a package that contains the ESLint config for the rest of the packages in the monorepo. This package has no need to depend on vitest except to satisfy peer dependency errors from eslint-plugin-vitest.

[veritem]

thank for bringing this up! it should be fixed in latest version.