Added LanguageAlpha2 and LanguageName types

[odelmarcelle]

Hello,

I was a bit disappointed that #141 did not implement alpha-2 languages codes, so here's my take at the implementation. Unlike #141, I tried to follow as closely as possible the existing implementation in country.py.

I thought that naming the types following convention in country.py was also much clearer than the obscure segmentation of the ISO 639 standards. Hence, I created two new types: LanguageAlpha2 and LanguageName and I would suggest refactoring ISO639_3 and ISO639_5 into LanguageAlpha3.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (e186814) to head (b735056).
Report is 13 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%            
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  Files           11        13     +2     
  Lines          685       817   +132     
  Branches       169       209    +40     
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+ Hits           685       817   +132     

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[yezz123]

LGTM 👍🏻

Thank you @odelmarcelle