capture screen of mac without selection

[dawei101]

No description provided.

[fritx]

Related: #4

If you want to take a full-screen screenshot, it might be good to have an option like { fullscreen: true }.

[uiur]

Thanks @fritx for your helpful comment.

Well, the interactive behavior in mac is right.
In Linux, import screenshot.png runs interactively, so I think it's better to keep it for consistency.

Maybe we should have an option like { interactive: true } or { fullscreen: true }.