Add date attributes to HTML extraction

[kernc]

As seen in, e.g.: https://www.aljazeera.com/news/2023/3/8/nato-cautious-amid-ongoing-nord-stream-blasts-investigation

Without this change, the time portion of the article is not found.

[adbar]

Hi @kernc, thanks for the PR!
I just made minor adjustments, is the PR ready to merge or do you have other attributes to add?

[codecov-commenter]

Codecov Report

Merging #73 (e434528) into master (5b9d47f) will not change coverage.
The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##           master      #73   +/-   ##
=======================================
  Coverage   98.19%   98.19%           
=======================================
  Files           8        8           
  Lines         942      942           
=======================================
  Hits          925      925           
  Misses         17       17           

Impacted Files	Coverage Δ
htmldate/core.py	97.97% <100.00%> (ø)

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[kernc]

Thanks. I was deferring while resolving some other issue while using htmldate via trafilatura (👏👏).
I don't have any others on my list at the moment, but will update when I do. Thanks!