Add Swift PM Support

Description

Add support for the Swift Package Manager (Swift PM).

Notes

• At the time of writing this ticket, Swift PM does not support explicitly including Apple modules as dependencies. This ticket should be blocked until we can specify both Foundation and UIKit.
• Swift PM also does not support including resources, which we use for our localized violation strings. See SR-2866: Need a way to include resources with targets.

SR-2866: Need a way to include resources with targets is still an open issue with SwiftPM.

SR-2866: Need a way to include resources with targets is still an open issue with SwiftPM.

There is now a Draft Proposal: Package Resources for SwiftPM. Still early days though!