Fix XcodeGen building after XcodeProj update to 8.8.0 (#1228)

* Fix XcodeGen building after XcodeProj update to 8.8.0

**Reason**
- XcodeProj has been updated and has API breaking changes

**Content**
- Added new enum case handling in `Linkage`
- Renamed the enum case name for `XCWorkspaceDataFileRef.init`

* add new product type to docs

* update changelog

Co-authored-by: Yonas Kolb <yonaskolb@users.noreply.github.com>