GH action tests for windows

[jdebacker]

This PR adds an OS matrix to the GH Action-run unit tests to ensure they are tested on Windows and Linux.

[codecov]

Codecov Report

Merging #22 (f28f283) into main (0d62697) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #22   +/-   ##
=======================================
  Coverage   54.38%   54.38%           
=======================================
  Files           4        4           
  Lines         114      114           
=======================================
  Hits           62       62           
  Misses         52       52           

Flag	Coverage Δ
unittests	54.38% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0d62697...f28f283. Read the comment docs.