Create CITATION.cff

[aaronspring]

Description

https://github.com/citation-file-format

Closes #344

[codecov]

Codecov Report

Merging #350 (4a96175) into main (6d2a98a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #350   +/-   ##
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  Coverage   94.58%   94.58%           
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  Files          24       24           
  Lines        2661     2661           
=======================================
  Hits         2517     2517           
  Misses        144      144           

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[aaronspring]

so for each release this CITATION file should be renewed (in theory), but this will be too much effort IMO. A JOSS paper sounds like a better reference in the long run, see #344