ports.7/history: Don't forget macOS!

Jordan Hubbard, one of the original authors of the FreeBSD
Ports Collection, later went on to create MacPorts, an evolution of
the idea written in TCL instead of Makefiles. Further, NetBSD's pkgsrc
is available natively on macOS. In either case, the idea of ports which
originated here spread to macOS. Note that in the HISTORY section.

MFC after: 3 days
Reviewed by: carlavilla,Jessica Hawkwell on Community Discord
Approved by: carlavilla (mentor)
Differential Revision: https://reviews.freebsd.org/D49205