Motivation for this change

To override the oh-my-zsh package easier (e.g. adding patches from the oh-my-zsh repo that weren't accepted yet) a package option is helpful.

Now sth. like this is possible:

{ pkgs, ... }:
{
  programs.zsh = {
    enable = true;
    ohMyZsh = {
      enable = true;
      package = pkgs.oh-my-zsh.overrideAttrs (a: { });
    };
  };
}

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.