Add CITATION file (#125)

Author: btschwertfeger

.github/CITATION

@@ -0,0 +1,9 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+- family-names: "Schwertfeger"
+  given-names: "Benjamin Thomas"
+  orcid: "https://orcid.org/0000-0001-7664-8434"
+title: "python-cmethods"
+doi: 10.5281/zenodo.7652755
+url: "https://github.com/btschwertfeger/python-cmethods"