Account for rare window shadow on Linux

[Avasam]

Describe the bug

Windows Shadows/Borders are a thing too on Linux. It seems kinda rare that's actually an issue. Might be so specific to just the finder that it's not even something I should bother with? Time will tell if users encounter this. Very low priority until an issue actually arise.

To Reproduce

an easy example is Finder in Ubuntu/GNOME . Simply use "Window selection" on it.

Expected behavior

Account for shadow when cropping, just like on Windows.

Screenshots and recordings

TODO if I can replicate it

Additional context

Extracted from #224