Add datacite - croissant mapping

[Daniel Garijo]

In https://raw.githubusercontent.com/Dans-labs/pyDataverse/croissant/src/mappings/dataverse_to_croissant.ttl by Slava Tykhonov (draft mapping)

[ljgarcia]

@dgarijo where should we add a link to this file and what would be the context?

[Daniel Garijo]

in the dataset union, we should add an equivalence based on the mapping, I believe. Especially since in the future we aim to use croissant as the main source.
Note that some elements are being extended with a croissant namespace instead of using schema.org