Samples: netcore on macOS should create a window
Problem to solve
Currently the netcore sample app on macOS is headless. This is fine, but would be better to have some video. libvlc cannot create a window by itself on mac, like it does on Windows. And a netcore app requires a bit more setup than a mono app to have a cocoa window https://docs.microsoft.com/en-us/xamarin/mac/app-fundamentals/console
Devs for testing netcore app users on mac.
improve the current sample.