starship: init module

[nezia1]

This PR adds a Starship module. Please keep in mind that shell support will need to be added once we get them into hjr. As per discussing it with @Lunarnovaa, a possible API we could use for it is:

# collection/programs/zsh.nix
  options.programs.zsh = {
  # ...
  integrations.starship = mkOption {
    default = programs.starship.enable;
  };
};

But this will do for now, since we do not have shells just yet.

• Ran nix fmt
• Tested the module locally

[Lunarnovaa]

pretty much lgtm