feat: data/MC ratio plot panel

[alexander-held]

Adding a ratio panel to the data/MC plots done with matplotlib in the contrib module.

[codecov]

Codecov Report

Merging #89 into master will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #89      +/-   ##
==========================================
+ Coverage   96.20%   96.30%   +0.10%     
==========================================
  Files          12       12              
  Lines         790      812      +22     
  Branches      104      105       +1     
==========================================
+ Hits          760      782      +22     
  Misses         28       28              
  Partials        2        2              

Impacted Files	Coverage Δ
src/cabinetry/contrib/matplotlib_visualize.py	100.00% <100.00%> (ø)

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