Add CITATION.cff

Signed-off-by: Vanessasaurus <814322+vsoch@users.noreply.github.com>

CITATION.cff

@@ -0,0 +1,23 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+- family-names: "Sochat"
+  given-names: "Vanessa"
+  orcid: "https://orcid.org/0000-0002-4387-3819"
+- family-names: "Muffato"
+  given-names: "Matthieu"
+  orcid: "https://orcid.org/0000-0002-7860-3560"
+- family-names: "Stott"
+  given-names: "Audrey"
+  orcid: "https://orcid.org/0000-0003-0939-3173"
+- family-names: "De La Pierre"
+  given-names: "Marco"
+  orcid: "https://orcid.org/0000-0002-7429-1846"
+- family-names: "Stuart"
+  given-names: "Georgia"
+  orcid: "https://orcid.org/0000-0003-2787-5299"
+title: "shpc-registry"
+version: 2023-03-08
+doi: 10.5281/zenodo.7709586
+date-released: 2023-03-11
+url: "https://github.com/singularityhub/shpc-registry"