v0.2.0

Added

• The export maps datePublished and contributor, with the same person sub-terms as
  author. CFF 1.2.0, Cargo.toml and pyproject.toml have no contributor list, so their rows are
  null; Zenodo's need a curated row, because its crosswalk cells are empty.

Changed

• The export's schema_version is 1.1, since it adds terms. A reader of 1.0 reads it unchanged.
• A consumer now needs rows only for the terms it uses, not for every term in the export.