Add support for swift package manager

[tc-sgupta]

No description provided.

[Oggerschummer]

I see issues with SPM in Xcode 12, it missing some information:

https://github.com/HeshamMegid/HMSegmentedControl has no Package.swift manifest for version 1.5.6

[o15a3d4l11s2]

@Oggerschummer, unfortunately it is not possible to use SPM with the released version, as you found out Package.swift is missing. The only solution (please note there might be future complications to using the master branch!) is to specify "master" as used branch when adding the package. Hopefully @HeshamMegid will make a new release, as the SPM change is already in master.