Add MinMaxDifferenceTransform

[Mr-Geekman]

Before submitting (must do checklist)

• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
• Did you update the CHANGELOG?

Proposed Changes

Look #952.

Closing issues

Closes #952.

[github-actions]

🚀 Deployed on https://deploy-preview-955--etna-docs.netlify.app

[codecov-commenter]

Codecov Report

Merging #955 (fea18ba) into master (76b8081) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #955      +/-   ##
==========================================
+ Coverage   85.38%   85.43%   +0.05%     
==========================================
  Files         148      148              
  Lines        7936     7951      +15     
==========================================
+ Hits         6776     6793      +17     
+ Misses       1160     1158       -2     

Impacted Files	Coverage Δ
etna/transforms/math/__init__.py	100.00% <100.00%> (ø)
etna/transforms/math/statistics.py	99.35% <100.00%> (+0.06%)	⬆️
etna/auto/runner/utils.py	100.00% <0.00%> (+50.00%)	⬆️

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