Add support for closed path fillet to Wire.fillet()

[dov]

This PR adds support for fillet of a closed wire to the Wire.fillet() method, by adding a fillet arc between the last and the first segments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.86%. Comparing base (f29f2d6) to head (d7b07a2).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1573   +/-   ##
=======================================
  Coverage   94.86%   94.86%           
=======================================
  Files          28       28           
  Lines        6226     6231    +5     
  Branches     1261     1264    +3     
=======================================
+ Hits         5906     5911    +5     
  Misses        193      193           
  Partials      127      127           

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[adam-urbanczyk]

LGTM, thanks!

[adam-urbanczyk]

@jmwright will you take a look? I had to replace some uses of typing_extensions.Literal with typing.Literal because of a unrelated osx failure. I do not fully understand why, but in general it is a change for better.

[jmwright]

+1 to merge

[adam-urbanczyk]

Thanks @dov !