Add citation.cff file

CITATION.cff

@@ -0,0 +1,15 @@
+cff-version: 1.2.0
+title: "Mermaid: Generate diagrams from markdown-like text"
+message: >-
+  If you use this software, please cite it using the metadata from this file.
+type: software
+authors:
+  - family-names: Sveidqvist
+    given-names: Knut
+  - name: "Contributors to Mermaid"
+repository-code: "https://github.com/mermaid-js/mermaid"
+url: "https://mermaid.js.org/"
+abstract: >-
+  JavaScript based diagramming and charting tool that renders Markdown-inspired
+  text definitions to create and modify diagrams dynamically.
+license: MIT