macOS: support native launch on login, quiet launch (launch without window), and hiding dock icon

[i0ntempest]

Or even better, runs in menu bar only, which makes sense for a server app.
I know electron might not support all of the above, so I'd at least hope you would add the ability to hide the dock icon.

[openspeedtest]

Desktop apps will soon feature an option like this. But this is much better #112 (comment)