Added citation file

CITATION.cff

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+# This CITATION.cff file was generated with cffinit.
+# Visit https://bit.ly/cffinit to generate yours today!
+
+cff-version: 1.2.0
+title: OpenSeadragon
+message: >-
+  If you use this software, please cite it using the
+  metadata from this file.
+type: software
+authors:
+  - given-names: Ian
+    family-names: Gilman
+    email: ian@iangilman.com
+  - given-names: Antoine
+    family-names: Vandecreme
+  - given-names: Mark
+    family-names: Salsbery
+  - given-names: Chris
+    family-names: Thatcher
+  - given-names:  Thomas
+    family-names: Pearce
+ identifiers:
+  - type: url
+    value: 'https://openseadragon.github.io/'
+    description: Homepage
+  - type: url
+    value: 'https://github.com/openseadragon/openseadragon'
+    description: Repository
+repository-code: 'https://github.com/openseadragon/openseadragon'
+url: 'https://openseadragon.github.io/'
+abstract: >-
+  An open-source, web-based viewer for high-resolution
+  zoomable images, implemented in pure JavaScript, for
+  desktop and mobile. 
+keywords:
+  - javascript
+  - image
+  - zooming
+  - viewer
+  - image-viewer
+  - high-resolution
+  - iiif
+license: BSD-3-Clause
+version: 4.1.1
+date-released: '2024-04-01'