Added FEH gtk-based light image viewer to ZaturaVM

[vadika]

Description of changes

Added FEH gtk-based light-footprint image viewer to ZaturaVM.
XDG handlers are coming in separate commit.

Checklist for things done

• [X ] Change can be updated with nixos-rebuild ... switch

Instructions for Testing

• List all targets that this applies to:
• Is this a new feature
  • List the test steps to verify:
• If it is an improvement how does it impact existing functionality?

[humaidq-tii]

If the goal is to run the image viewer on zathura-vm, then there should be some automatic copy mechanism when someone opens an image on other VMs.

Because currently, zathura-vm doesn't use storagevm mounts.

[milva-unikie]

Before the XDG handlers are added I don't think it makes sense to add this. Tested on Lenovo-X1 that there is now Image Viewer icon, but it does not open the app. Is the icon is even going to be needed if the images are supposed to open automatically in the app?