Support for Swift Package Manager

[NathanWalker]

Is your feature request related to a problem? Please describe.

Right now you have to manually modify the xcodeworkspace to include swift packages.

Describe the solution you'd like

Ability to add App_Resources/iOS/swift-packages.txt or .yml file with lists the git url's to Swift Packages.

CLI would pick it up and modify the xcodeproj to include them inherently.

Could also potentially have a command that adds them to such a file if needed: ns add swift-package (url)

References:
https://www.swift.org/package-manager/
For example ability to include this: https://github.com/apple/swift-markdown

Describe alternatives you've considered

No response

Anything else?

No response

Please accept these terms

• I have searched the existing issues as well as StackOverflow and this has not been posted before
• I agree to follow this project's Code of Conduct

[NathanWalker]

Extra consideration:

• Support from plugins
• If a newer version came in from a plugin and same SPM existed in local project, and cli merges, we need a way to specify resolution (which one should override)

[NathanWalker]

Released with 8.5