Add support for Cygwin

[500-internal-server-error]

Noticed uu-uname was printing the OS as "unknown" :)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.75%. Comparing base (bad3b54) to head (24d2722).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #102   +/-   ##
=======================================
  Coverage   93.75%   93.75%           
=======================================
  Files           5        5           
  Lines         784      784           
=======================================
  Hits          735      735           
  Misses         49       49           

Flag	Coverage Δ
macos_latest	99.35% <ø> (ø)
ubuntu_latest	99.37% <ø> (ø)
windows_latest	92.99% <ø> (ø)

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[cakebaker]

Thanks for your PR!