Add display handling.

[musically-ut]

This starts dealing with #40.

I'm not sure whether there is an easy way of turning mirroring on/off or setting resolutions, other than including binaries.

[doodzik]

you can monitor changes to your config with this command:
sudo opensnoop -n cfprefsd-int-int
Maybe this will help you.

[musically-ut]

@doodzik I'm afraid I don't follow. Did you mean to comment on this issue?

[rgcr]

Thank you so much for your contribution 👍