Stop appending wind_speed_unit in weather.forecast_home value to avoid
duplicating units (the attribute already supplies the units). Also add
libwebp to the kemptop package list for WebP image support.
Rename group "libvirt" to "libvirtd".
Add diffoscope and nix-index to systemPackages.
Replace hplipWithPlugin with hplip.
Enable spice USB redirection and add pkgs.virtiofsd to
virtualisation.libvirtd.qemu.vhostUserPackages.
