Closes: #157
XDG portals expose a D-Bus interface allowing apps to prevent screen
idling, user switching, and other actions. That interface,
org.freedesktop.portal.Inhibit, does all of the heavy lifting here.
Idling = the screen dimming or shutting off.
Idling is inhibited when a video is actively playing.
Idling is NOT inhibited when videos aren't playing - this includes
paused or stopped videos.
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