Add dev/zsh module & zunit package

modules/dev/zsh.nix

@@ -0,0 +1,8 @@
+{ config, lib, pkgs, ... }:
+
+{
+  my.packages = with pkgs; [
+    shellcheck
+    (callPackage (import <my/packages/zunit.nix> {}))
+  ];
+}

packages/zunit.nix

@@ -0,0 +1,25 @@
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  version = "0.8.2";
+  pname = "zunit";
+
+  src = fetchurl {
+    url = "https://github.com/zunit-zsh/zunit/releases/download/v${version}/zunit";
+    sha256 = "1bmp3qf14509swpxin4j9f98n05pdilzapjm0jdzbv0dy3hn20ix";
+  };
+
+  phases = "installPhase";
+
+  installPhase = ''
+    outdir=$out/share/zunit
+    mkdir -p $outdir
+    cp $src $outdir/antigen.zsh
+  '';
+
+  meta = {
+    description = "ZUnit is a powerful unit testing framework for ZSH";
+    homepage = https://zunit.xyz/;
+    license = stdenv.lib.licenses.mit;
+  };
+}