Necessary due to it looking like [SPDX](https://github.com/spdx/license-list-XML/issues/1393) might not approve the 3.0.0 version. The 2.1.0 version will have to suffice as a safe fallback which won't cause conflicts with downstream tooling.
Necessary allow academics and researchers to reference this project. [Documentation](https://citation-file-format.github.io).
