Add CITATION.cff file

CITATION.cff

@@ -0,0 +1,20 @@
+cff-version: 1.2.0
+message: If you use this software in a publication, please cite it using these metadata.
+title: Movement
+abstract: Mesh movement methods for finite element problems solved using Firedrake.
+authors:
+ - family-names: Wallwork
+ given-names: Joseph G.
+ orcid: "https://orcid.org/0000-0002-3646-091X"
+ - family-names: Kramer
+ given-names: Stephan C.
+ orcid: "https://orcid.org/0000-0002-9193-5092"
+ - family-names: Zhang
+ given-names: Mingrui
+ - family-names: Dundovic
+ given-names: Davor
+ orcid: "https://orcid.org/0009-0000-6085-4794"
+version: 0.2
+date-released: "2024-05-22"
+license: MIT
+repository-code: "https://github.com/mesh-adaptation/movement"