feat(cron): add support for day-of-week special characters

[reugn]

Implement support for L (last day) and # (nth day) special characters in the cron day-of-week field.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 92.68293% with 3 lines in your changes missing coverage. Please review.

Project coverage is 94.83%. Comparing base (9dff931) to head (5e9fff0).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
quartz/cron.go	92.10%	2 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #150      +/-   ##
==========================================
+ Coverage   94.44%   94.83%   +0.39%     
==========================================
  Files          19       19              
  Lines        1152     1182      +30     
==========================================
+ Hits         1088     1121      +33     
+ Misses         47       45       -2     
+ Partials       17       16       -1     

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