Support for distribution via Swift Package Manager

[eneko]

Swift Package Manager is included with Xcode since version 11, as the default package manager for dependencies. Contrary to its name, it can also package Obj-c libraries like XLForm.

I would like to submit a Pull Request to add support for SwiftPM. However, a few changes are needed:

• Add Package.swift to the repo
• Flatten directory structure (this is so header files can properly be found by Xcode when building applications using XLForm)
• No updates to XLForm Xcode project, other than references to the new file locations on disk.

I have a fork working with SwiftPM, but before finishing the work, I was hoping to get feedback if this is something the repo owners are willing to add. I feel adding SwiftPM on top of CocoaPods and Carthage is a good step forward.

Thanks, Eneko

[eneko]

@mats-claassen @mtnbarreto, I've pushed a PR (#1073) with these changes, in case you were interested. Please let me know/

[eneko]

This has now been resolved and released in 4.2.0