[RFC]Fix end of the week when the date provider is the end of the week

[rntdrts]

When the date provided is the end of the week we should return that same date, with the end of the week format.

This should fix this 👉 #61

[codecov]

Codecov Report

Merging #66 (ce063dd) into master (3a86b77) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
+ Coverage   89.08%   89.11%   +0.03%     
==========================================
  Files           3        3              
  Lines         632      634       +2     
==========================================
+ Hits          563      565       +2     
  Misses         44       44              
  Partials       25       25              

Impacted Files	Coverage Δ
carbon.go	90.46% <100.00%> (+0.03%)	⬆️

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