feat: enable use as a screensaver
Recovery of !184 (closed), because the fork hosting the changes for the MR was deleted.
The screen locker is already in essence a screensaver, allowing one to hide the unlock controls and clock, show various types of wallpaper slideshows, etc. This is great since screensavers are almost non-existent these days, and they are still wanted by many people.
The only thing missing really is the ability to use it as a screensaver without requiring a password to unlock.