Create CITATION.cff

CITATION.cff

@@ -0,0 +1,15 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+- family-names: "Busecke"
+  given-names: "Julius J. M."
+  orcid: "https://orcid.org/0000-0001-8571-865X"
+- family-names: "Martin"
+  given-names: "Julius J. M."
+  orcid: "https://orcid.org/0000-0001-8571-865X"
+- family-names: "Abernathey"
+  given-names: "Ryan P."
+  orcid: "https://orcid.org/0000-0001-5999-4917"
+title: "aerobulk-python"
+url: "https://github.com/xgcm/aerobulk-python"
+# version and doi are completed by Zenodo automatically, do not provide here.