Create CITATION.cff

Thanks to @zachcran for the content.

CITATION.cff

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+cff-version: "1.2.0"
+authors:
+- family-names: Butler
+  given-names: Branden
+- family-names: Richard
+  given-names: Ryan M.
+  orcid: "https://orcid.org/0000-0003-4235-5179"
+contact:
+- family-names: Richard
+  given-names: Ryan M.
+  orcid: "https://orcid.org/0000-0003-4235-5179"
+doi: 10.5281/zenodo.7116601
+message: If you use this software, please cite our article in the
+  Journal of Open Source Software.
+preferred-citation:
+  authors:
+  - family-names: Butler
+    given-names: Branden
+  - family-names: Richard
+    given-names: Ryan M.
+    orcid: "https://orcid.org/0000-0003-4235-5179"
+  date-published: 2022-09-23
+  doi: 10.21105/joss.04680
+  issn: 2475-9066
+  issue: 77
+  journal: Journal of Open Source Software
+  publisher:
+    name: Open Journals
+  start: 4680
+  title: "CMinx: A CMake Documentation Generator"
+  type: article
+  url: "https://joss.theoj.org/papers/10.21105/joss.04680"
+  volume: 7
+title: "CMinx: A CMake Documentation Generator"