Document refrence type mapping funtionality

[billybonks]

This feature was introduced with #42, would be great for us to document it :)

[mansona]

Does #45 not cover the docs enough for you? 🤔

I think I might not have released it to npm so if you were checking the changelog there it won't have been updated. let me know if that covers what you expect and I'll get it released straight away 👍