create citation cff file

CITATION.cff

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+cff-version: 1.2.0
+message: "If you use this training material, please cite it as below."
+type: software
+authors:
+- family-names: Karoune
+  given-names: Emma
+  affiliation: The Alan Turing Institure
+  orcid: 'https://orcid.org/0000-0002-6576-6053'
+- family-names: Kerfant
+  given-names: Celine
+  affiliation: Universitat Pompeu Fabra
+  orcid: 'https://orcid.org/0000-0002-4297-5469'
+title: International Committee on Open Phytolith Science Training Resources
+version: 1.0.0
+doi: 10.5281/zenodo.1234
+date-released: 2022-04-06
+url: "https://github.com/open-phytoliths/ICOPS-training-2022"
+abstract: >-
+  This is an archive of the repository of training material from workshops and other training events organised and run by the International Committee on Open Phytolith Science. 
+keywords:
+  - Phytoliths
+  - Archaeobotany
+  - Open Science
+  - Open Data
+  - Open Access
+  - Open Source
+license: CC-BY-4.0