RF: Use comma not tab in produced image03.csv file

[yarikoptic]

TODOs

• some primitive test

[codecov]

Codecov Report

Merging #21 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master      #21   +/-   ##
=======================================
  Coverage   14.61%   14.61%           
=======================================
  Files           2        2           
  Lines         219      219           
=======================================
  Hits           32       32           
  Misses        187      187

Impacted Files	Coverage Δ
bids2nda/main.py	13.02% <0%> (ø)	⬆️

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[yarikoptic]

well, according to NDAR/nda-tools#13 (comment) TSV was not supported and thus I went for .csv, but I wonder if it is still needed and either we might just want to make it an option?