[jackpot51]

Continuation of #1875 , with some additional cleanup

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[jklgrasso]

Thumbnails look good. Thumbnails for images, videos, and other types work as expected, including desktop icons.

[Milli189]

this should probably be added to cosmic panel as well as other cosmic components, so every component can show the icon of an open .exe app, like apps running in wine and certain windows games that don't have a .desktop file