build for latest iOS/watchOS

[cbaker6]

Separated out this PR for easier review.

• [x] Bumps CI to Xcode 14, iOS 16, watchOS 9.0
• [x] Fix Xcode 14 warnings about switching open->public
• [x] Fix library evolutionary support warnings in workspace build
• [x] Enable async/await methods on iOS13+ and watchOS6+
• [x] Minimum deployment of watchOS is 6.0 since there's no dependencies on a higher OS
• [x] Bump minimum tools in Package.swift to 5.5 since the async/await methods requires this as a minimum. This also always for DocC documentation to be added. I'm assuming a lot of the README can be copied to DocC in the future, but I didn't add any of these files
• [x] Removed periods at the end of bullet points in README
• [x] Add watchOS builds to CI to protect against breaking PR's. These should be able to run tests in Xcode 13, but the Xcode project isn't configured for this
• [x] allow OCKCalendarController and OCKWeekCalendarController view models to build on watchOS. These were importing UIKit, but can import CoreGraphics instead
• [x] Add .spi.yml for properly building on Swift Package Index. Swift Package Index is the successor of SwiftPM Library. Also added badges:

Note1: The watchOS platform should appear after this PR is merged to the main as the added .spi.yml tells Swift Package Index what scheme to use for building watch.

[cbaker6]

@gavirawson-apple when you get a chance, take a look and let me know if any more changes are needed

[cbaker6]

@gavirawson-apple I updated the list of changes to the repo