Add fold(Right) and reduce(Right) tests

[passsy]

No description provided.

[codecov]

Codecov Report

Merging #41 into master will increase coverage by 3.19%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #41      +/-   ##
==========================================
+ Coverage   81.15%   84.35%   +3.19%     
==========================================
  Files          25       25              
  Lines        1502     1502              
==========================================
+ Hits         1219     1267      +48     
+ Misses        283      235      -48

Impacted Files	Coverage Δ
lib/src/extension/iterable_extension_mixin.dart	75.82% <0%> (+3.3%)	⬆️
lib/src/extension/list_extension_mixin.dart	90.29% <0%> (+25.24%)	⬆️

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