Start Trayscale in tray at startup

[serverless83]

Hi, since the new tray icon has been introduced, would it be possible to have an option to automatically start Trayscale minimized in the traybar at startup?

[DeedleFake]

That's an excellent idea. I'd actually quite like that, too.

I'm planning on adding an actual configuration system at some point, but for now I think I can do that with a command-line argument.