test(ini): add line break and whitespace tests

[timreichen]

Ref https://github.com/denoland/std/pull/6515/files#r2015266070

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.31%. Comparing base (61f9fd3) to head (cc75c1f).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6519      +/-   ##
==========================================
+ Coverage   95.29%   95.31%   +0.01%     
==========================================
  Files         576      576              
  Lines       43315    43315              
  Branches     6477     6478       +1     
==========================================
+ Hits        41279    41287       +8     
+ Misses       1995     1988       -7     
+ Partials       41       40       -1     

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[kt3k]

LGTM