feat(core): add Quick/Nimble *Spec.swift to Swift group

Quick is the Swift ecosystem's RSpec analogue — the dominant BDD-style
testing framework before Apple shipped Swift Testing (Xcode 16, 2024).
Files follow the `<Subject>Spec.swift` convention and typically live
under `<Package>Tests/` (SPM) or `<AppName>Tests/` (Xcode) alongside
XCTest files, so the dir rules do catch most of them — but small
gem-style packages and CLI tools sometimes keep `*Spec.swift` at the
`Sources/` root, which the dir rules miss.

Kept as a separate opt-in glob from `*Tests.swift` so users on
XCTest-only projects (Apple's official Swift repos, Alamofire) aren't
carrying a comment for a framework they don't use. Mirrors the split
in the Ruby group between RSpec `*_spec.rb` and Minitest `*_test.rb`.