nix: add packaging; update devshell

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I9f1ddf6dbd141b5a85b4b5a36c2c9a586a6a6964

flake.nix

@@ -1,7 +1,11 @@
 {
-  description = "Wayland Wallpaper Daemon";
+  description = "Super-fast, lightweight and efficient wallpaper daemon for Wayland compositors";
   inputs.nixpkgs.url = "github:NixOS/nixpkgs?ref?nixos-unstable";
-  outputs = {nixpkgs, ...}: let
+  outputs = {
+    nixpkgs,
+    self,
+    ...
+  }: let
     systems = ["x86_64-linux" "aarch64-linux"];
     forAllSystems = f:
       builtins.listToAttrs (map (system: {
@@ -17,5 +21,12 @@
     in {
       default = pkgs.callPackage ./shell.nix {};
     });
+
+    packages = forAllSystems (system: let
+      pkgs = pkgsFor system;
+    in {
+      chroma = pkgs.callPackage ./nix/package.nix {};
+      default = self.packages.${system}.chroma;
+    });
   };
 }