[docs] Classifiers tutorial

[jd-foster]

Adding this initial draft here to get any feedback.

Preview https://jump.dev/JuMP.jl/previews/PR3569/tutorials/nonlinear/classifiers/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b13812d) 98.38% compared to head (48d6d0e) 98.38%.
Report is 2 commits behind head on master.

Additional details and impacted files

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  Coverage   98.38%   98.38%           
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  Files          37       37           
  Lines        5624     5629    +5     
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+ Hits         5533     5538    +5     
  Misses         91       91           

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[odow]

Is it ready for me to take another look? Or do you still have more plans

[jd-foster]

Please. No, this is as much as I want to do.

[odow]

Okay, @jd-foster I made a number of changes, mainly to simplify the code (returning a classifier function) and simplify the plotting calls (at the expense of less control over the colors, etc).

[jd-foster]

Thanks @odow , looks good to me.

[jd-foster]

(though a bit sad that my carefully curated colour design has been thrown out 😄)

[odow]

I have wondered about standardizing all of the plots used across the documentation...