Create CITATION.cff on JOSS acceptance

CITATION.cff

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+cff-version: "1.2.0"
+authors:
+- family-names: Kingsbury
+  given-names: Ryan
+  orcid: "https://orcid.org/0000-0002-7168-3967"
+doi: 10.5281/zenodo.8332915
+message: If you use this software, please cite our article in the
+  Journal of Open Source Software.
+preferred-citation:
+  authors:
+  - family-names: Kingsbury
+    given-names: Ryan
+    orcid: "https://orcid.org/0000-0002-7168-3967"
+  date-published: 2024-03-25
+  doi: 10.21105/joss.06295
+  issn: 2475-9066
+  issue: 95
+  journal: Journal of Open Source Software
+  publisher:
+    name: Open Journals
+  start: 6295
+  title: "pyEQL: A Python interface for water chemistry"
+  type: article
+  url: "https://joss.theoj.org/papers/10.21105/joss.06295"
+  volume: 9
+title: "pyEQL: A Python interface for water chemistry"