fix: Ensure uncertainty bars don't extend below 0

[matthewfeickert]

Resolves #41

* Ensure the bottom of uncertainty bars don't extend below 0
   - Avoid axis limits dropping below 0
* Rebin example histograms
   - Avoid running into range limitations of ATLAS Style
* Set lower bound on hist to v2.2.0
   - Pickup boost-histogram v1.0 and mplhep v0.2.16+
* Add VS Code settings to gitignore

Huge thanks goes out to @henryiii and @andrzejnovak for their impressive work on hist and mplhep!

[codecov]

Codecov Report

Merging #47 (79185bc) into master (5daa77a) will decrease coverage by 0.26%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
- Coverage   28.09%   27.83%   -0.27%     
==========================================
  Files           7        7              
  Lines         210      212       +2     
  Branches       39       39              
==========================================
  Hits           59       59              
- Misses        151      153       +2     

Flag	Coverage Δ
unittests	27.83% <0.00%> (-0.27%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/heputils/plot.py	18.88% <0.00%> (-0.22%)	⬇️

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