Kiosk mode

[SO9010]

This is a PR for issue #528. It is essentially done and can be run by adding the system command psst-gui -- --k or psst-gui -- --kiosk to run in kiosk mode.

What I have implemented is that it opens everything in full screen without window decorations. Additionally, the settings are shown directly after logging in with a button to close it, so the settings are set but cannot be changed as I removed the button to access settings.

I have it so that when this kiosk mode is enabled, the keyboard shortcuts don't work (even though they also only work on Mac), and it cannot be exited in this way.

I think that the keyboard shortcuts to access the desktop need to be done on the system level because I can't interrupt things like clicking the super key. Correct me if I'm wrong. If I'm not, this should be ready to be merged with the MR with @jacksongoode's approval.

[jacksongoode]

This doesn't appear to fullscreen on macOS. I'm trying to figure out why. I just get a borderless small window.

[jacksongoode]

@SO9010 I made a few tweaks so that on macOS this works. I've also confirmed that the binary can be run as psst-gui -k or psst-gui --kiosk. Happy to merge if those changes look good on Windows and Linux for you

[jacksongoode]

Approved, pending your final check.

[SO9010]

This doesn't appear to fullscreen on macOS. I'm trying to figure out why. I just get a borderless small window.

Heya same issue on Linux!

[SO9010]

Need to lint I'll do that tomorrow evening.

[jacksongoode]

Linted, should be good!

[SO9010]

So I believe there is not way to get this to actually work for the raspberry pi due to upstream limitations.

But as it still works for windows and Mac do you think we should still merge it then I could detail how to get it working on any Linux system (by using a different window manager). Maybe as suggested we should rename this to --start-maximize. We could perhaps then add other options like --no-prefrence-cog and then --no-title-bar and we mention the limitations that on some systems it will still show the title bar.

What do you think @jacksongoode