WIP: Refactor project into Swift Package

[kevinrpb]

• Created a SPM package and set the ModalView part as a framework so that it can be imported from Xcode 11 as a dependency

• Move the former project into another target as a demo

Let me know what you think and/or if I should change anything =D

[kevinrpb]

~Closed it because I noticed something else needing refactor in order to use as framework. Wille reopen when I finish it~

Hey, @cyrilzakka, I got most of it working. However, I'm having some problems with the transformation applied when the modal is open.

It seems that when I try to change the modal position from outside, it won't detect the needed offset / opacity correctly. Do you have a moment to help me solve this? 😀

[cyrilzakka]

Will definitely take a look at this as soon as possible! Thank you for your work!