After download the project kindly add PartialSheet package:
In Xcode 11 or grater, in you project, select: File > Swift Packages > Add Pacakage Dependency.
In the search bar type PartialSheet and when you find the package, with the next button you can proceed with the installation.
If you can't find anything in the panel of the Swift Packages you probably haven't added yet your github account. You can do that under the Preferences panel of your Xcode, in the Accounts section.