Deprecation of the Cordova OSX Platform

[Niklas Merz <ni...@apache.org>]

We are hereby announcing the deprecation of cordova-osx.

This means that the Cordova development community will not be doing any
more work on this platform. Please migrate to the cordova-electron
platform or try Mac Catalyst with the cordova-ios platform.

The usage and activity around the osx platform have been quite low for a
long time. Cordova's other solutions for building apps for macOS are
actively maintained and especially cordova-ios offers better plugin
support.

The npm package has been marked as deprecated and all necessary steps
for the deprecation have been completed.