add min/maximum(abs)

[aplavin]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 84.37500% with 5 lines in your changes missing coverage. Please review.

Project coverage is 96.65%. Comparing base (13c76e1) to head (266082c).
Report is 17 commits behind head on master.

Files with missing lines	Patch %	Lines
src/IntervalSets.jl	84.37%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #196      +/-   ##
==========================================
- Coverage   99.11%   96.65%   -2.46%     
==========================================
  Files           6        6              
  Lines         225      299      +74     
==========================================
+ Hits          223      289      +66     
- Misses          2       10       +8     

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[hyrodium]

I just added a comment to improve the test coverage. Other changes look great to me!