libappimage: add missing xz dependency

pkgs/by-name/li/libappimage/package.nix

···
   librsvg,
   squashfuse,
   xdg-utils-cxx,
+  xz, # for liblzma
   zlib,
 }:
 stdenv.mkDerivation rec {
···
     libarchive
     squashfuse
     xdg-utils-cxx
+    xz
   ];
 
   propagatedBuildInputs = [