Added ForkParent struct to show details of a project if it is a fork. (#168)
Added ForkParent struct to show details of a project if it is a fork. (#168)

If a project is a fork it will show the details of the project that
it was forked from.

If a project isn't a fork the setting will be null.
mickymiek/go-gitlab,xanzy/go-gitlab,samuelthomps0n/go-gitlab,nyxi/go-gitlab