add swiftlint

[joshuah345]

All Submissions

• [x] Have you made sure there aren't any other open Pull Requests for the same update/change?
• [ ] This Pull Request doesn't contain any package additions; it's a small change (e.g README change)

Package Additions/Updates

• [ ] ~~Have you confirmed this builds & works as intended on an iOS device (if applicable)?~~
• [x] Have you confirmed this builds & works as intended on a macOS device (if applicable)?

iOS build currently isn't possible due to one of the project's dependencies using Process() which isn't available on iOS.