NF: add zenodo files

[skoudoro]

all in the title, add zenodo files for release citation.

Zenodo has been activated:

related to #110

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.50%. Comparing base (4bdd8a8) to head (988a36e).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #111   +/-   ##
=======================================
  Coverage   61.50%   61.50%           
=======================================
  Files          13       13           
  Lines        2613     2613           
=======================================
  Hits         1607     1607           
  Misses       1006     1006           

Flag	Coverage Δ
unittests	61.50% <ø> (ø)

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