Fixes Swift Package Manager Support

[swhitty]

Updates Headers to only expose publicly;

• Bagel.h
• BagelCarrierDelegate.h
• BagelConfiguration.h
• BagelDeviceModel.h
• BagelProjectModel.h

All other headers are project headers with forward declarations are added where required.

Adds support for macOS targets so that you can test the packages with with % swift build

[mran3]

I like Bagel, I want to be able to use it with Swift Package Manager. I hope this fixes it :)

[mran3]

I managed to make this work, If anyone needs it, as a workaround, it can be used via SPM from my repo:
https://github.com/mran3/Bagel
I basically did nothing, just merged @swhitty PR with the main branch of this project. All credits to him and @yagiz for this great project. I hope it gets active again.

[filimo]

@mran3 You can find other fixes here https://github.com/ricobeck/Bagel.git

[Abanoub-Yassir]

@yagiz please accept this so we can use your library by SPM

[watanak]

why I still got error with Bagel/BagelBaseModel.h' file not found when I try to build it? Please help me a bit.