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.
`lazy_static` and `smol_str` weren't used. COSMIC Player used `dirs`
once to find the user's home directory. Rust fixed and undeprecated its
`home_dir` function in 1.85, which released earlier this year and is the
MSRV of libcosmic.
