Hide while an app is fullscreen on the same monitor

[danielchalmers]

• The widget hides while a game, video, or slideshow is fullscreen on its monitor and comes back when that ends, in the same place and without taking focus. Readings and the graph keep updating while it's hidden.
• It checks when the foreground window changes and on the existing one-second tick, so a browser video going fullscreen is caught within a second. There's no new timer.
• Only the widget's monitor counts. A fullscreen video there keeps it hidden while you work on another monitor, and slides on a projector hide it while Presenter View has focus. Maximized windows with a title bar, the desktop, taskbar, Alt+Tab, and Task View don't trigger it.
• Starting the exe again shows it over the fullscreen app until that app is focused again. Right-click → "Hide when fullscreen", under "Always on top", turns it off.

Release notes: "Hide when fullscreen" is on by default, including for existing settings files.