adding a citation file

CITATION.cff

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+# This CITATION.cff file was generated with cffinit.
+# Visit https://bit.ly/cffinit to generate yours today!
+
+cff-version: 1.2.0
+title: 'CREMMA-AN-TestamentDePoilus '
+message: >-
+  If you use this dataset, please cite it using the metadata
+  from this file.
+type: dataset
+authors:
+  - given-names: Alix
+    family-names: Chagué
+    affiliation: ALMAnaCH, Inria Paris
+    orcid: 'https://orcid.org/0000-0002-0136-4434'
+  - given-names: Thibault
+    family-names: Clérice
+    affiliation: Centre Jean Mabillon
+    orcid: 'https://orcid.org/0000-0003-1852-9204'
+  - given-names: Anaïs
+    family-names: Mazoue
+  - given-names: Elsa
+    family-names: Van Kote
+license: CC-BY-4.0
+repository-code: 'https://github.com/HTR-United/CREMMA-AN-TestamentDePoilus'
+keywords:
+  - HTR
+  - WWI
+  - French
+  - manuscripts
+  - Archives