fix(ordinal): accept eighth instead of eight as an ordinal

[anasbekheit]

The ordinal table had "eight" instead of "eighth", so eighth monday was rejected while eight monday was accepted. GNU date accepts eighth.

[anasbekheit]

@cakebaker I think this fix may improve test parity with GNU

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.74%. Comparing base (e25bf15) to head (80047a4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #333      +/-   ##
==========================================
+ Coverage   97.48%   97.74%   +0.25%     
==========================================
  Files          21       21              
  Lines        4258     4293      +35     
  Branches      136      136              
==========================================
+ Hits         4151     4196      +45     
+ Misses        106       96      -10     
  Partials        1        1              

Flag	Coverage Δ
macos_latest	97.74% <100.00%> (+0.25%)	⬆️
ubuntu_latest	97.74% <100.00%> (+0.25%)	⬆️
windows_latest	12.06% <0.00%> (-0.10%)	⬇️

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[anasbekheit]

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

[codspeed]

Merging this PR will degrade performance by 3.19%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 20 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	parse_invalid_input	59 µs	61 µs	-3.19%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing anasbekheit:fix/ordinal-eighth (80047a4) with main (e25bf15)}