Add "light" package and setuid wrapper

pkgs/os-specific/linux/light/default.nix

@@ -0,0 +1,20 @@
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  version = "0.9";
+  name = "light-${version}";
+  src = fetchurl {
+    url = "https://github.com/haikarainen/light/archive/v${version}.tar.gz";
+    sha256 = "1dnzkkg307izvw76gvzsl2vpxd2a1grxg5h82ix505rb9nnmn0d6";
+  };
+
+  installPhase = "mkdir -p $out/bin; cp light $out/bin/";
+
+  meta = {
+    description = "GNU/Linux application to control backlights";
+    homepage = https://haikarainen.github.io/light/;
+    license = stdenv.lib.licenses.gpl3;
+    maintainers = with stdenv.lib.maintainers; [ puffnfresh ];
+    platforms = stdenv.lib.platforms.linux;
+  };
+}