Add CITATION.cff file

[cgobat]

Resolves #460.

Feel free to make updates as you see fit—I sourced this info from the existing codemeta.json and the JOSS publication itself.

[codecov[bot]]

Codecov Report

Merging #465 (7f25718) into main (141fe4d) will increase coverage by 0.00%. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #465   +/-   ##
=======================================
  Coverage   99.86%   99.86%           
=======================================
  Files          13       13           
  Lines       15633    15640    +7     
=======================================
+ Hits        15612    15619    +7     
  Misses         21       21           

see 1 file with indirect coverage changes

[cgobat]

Anything else you wanted to see here, @AndrewAnnex?