qview: fix build on darwin, support extra formats

Clarified license to GPL3+.
Building on darwin requires qtsvg.
qtimageformats adds support for extra image formats, such as WebP.

pkgs/applications/graphics/qview/default.nix

···
-{ mkDerivation, lib, fetchFromGitHub, qmake, qtbase }:
+{ lib
+, mkDerivation
+, fetchFromGitHub
+, qmake
+, qtbase
+, qtimageformats
+, qtsvg
+}:
 
 mkDerivation rec {
   pname = "qview";
···
 
   buildInputs = [
     qtbase
+    qtimageformats
+    qtsvg
   ];
 
   patchPhase = ''
···
   meta = with lib; {
     description = "Practical and minimal image viewer";
     homepage = "https://interversehq.com/qview/";
-    license = licenses.gpl3;
+    license = licenses.gpl3Plus;
     maintainers = with maintainers; [ acowley ];
     platforms = platforms.all;
   };