Previous attempt failed by design of `npm pack` / `npm publish`,
as documented at https://docs.npmjs.com/cli/v6/configuring-npm/package-lock-json :
> One key detail about package-lock.json is that it cannot be published,
> and it will be ignored if found in any place other than the toplevel
> package. It shares a format with npm-shrinkwrap.json, which is
> essentially the same file, but allows publication.
>
> This is not recommended unless deploying a CLI tool or otherwise using
> the publication process for producing production packages.
, and we are a CLI tool. Switching to shrinkwrap.
