Make the stockfish software more easily citable, for example in academic papers.
fixes https://github.com/official-stockfish/Stockfish/issues/4419
closes https://github.com/official-stockfish/Stockfish/pull/4422
No functional change
--- /dev/null
+# This CITATION.cff file was generated with cffinit.
+# Visit https://bit.ly/cffinit to generate yours today!
+
+cff-version: 1.2.0
+title: Stockfish
+message: >-
+ Please cite this software using the metadata from this
+ file.
+type: software
+authors:
+ - name: The Stockfish developers (see AUTHORS file)
+repository-code: 'https://github.com/official-stockfish/Stockfish'
+url: 'https://stockfishchess.org/'
+repository-artifact: 'https://stockfishchess.org/download/'
+abstract: Stockfish is a free and strong UCI chess engine.
+keywords:
+ - chess
+ - artificial intelligence (AI)
+ - tree search
+ - alpha-beta search
+ - neural networks (NN)
+ - efficiently updatable neural networks (NNUE)
+license: GPL-3.0