I imagine anyone using this library will already be installing immutable.js so maybe you should have it as peerDependency so the same install is used in this package.
I have bad memories of peer deps from npm 2 days. But I suppose in this case, it would always be better to grab the peer dep than to end up with two versions of immutable.
I imagine anyone using this library will already be installing immutable.js so maybe you should have it as peerDependency so the same install is used in this package.