fix(weekday): accept a period after abbreviated weekday names

[anasbekheit]

The weekday parser matched with alpha1, which never consumes ., so the existing "mon.", "tue.", … arms could never match and inputs like mon. or wed., 2024-01-03 were rejected. GNU date accepts a period after the three-letter abbreviation. The parser now includes an optional trailing period in the word.

[anasbekheit]

@cakebaker I think this PR may improve GNU test parity.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.71%. Comparing base (701f5a0) to head (6943f5d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #334      +/-   ##
==========================================
+ Coverage   97.70%   97.71%   +0.01%     
==========================================
  Files          21       21              
  Lines        4395     4418      +23     
  Branches      138      138              
==========================================
+ Hits         4294     4317      +23     
  Misses        100      100              
  Partials        1        1              

Flag	Coverage Δ
macos_latest	97.71% <100.00%> (+0.01%)	⬆️
ubuntu_latest	97.71% <100.00%> (+0.01%)	⬆️
windows_latest	12.33% <4.16%> (-0.07%)	⬇️

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[sylvestre]

please add a test with the full parser, like parse_datetime("wed., 2024-01-03")
the existing "mon." unit tests already passed before, they don't check that the whole input was consumed

[anasbekheit]

Added a new commit

[anasbekheit]

Are there any concerns blocking the merge of this PR?
@sylvestre @xtqqczze

[anasbekheit]

branch is rebased, with issues addressed @sylvestre