Overfitting/Underfitting tutorial

[gtduncan]

Describe your changes

Tutorial on underfitting/overfitting implementing learning curves created by sk-eval

Issue ticket number and link

Closes #197

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I have added thorough tests (when necessary).
• [x] I have added the right documentation in the docstring and changelog (when needed)

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:books: Documentation preview :books:: https://sklearn-evaluation--299.org.readthedocs.build/en/299/

[coveralls]

Pull Request Test Coverage Report for Build 4296827765

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 90.93%

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Totals
Change from base Build 4296301858:	0.0%
Covered Lines:	3118
Relevant Lines:	3429

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💛 - Coveralls

[gtduncan]

Just made those changes!

[idomic]

@gtduncan please resolve the CHANGELOG.md conflicts so we can merge.

[idomic]

Nice job @gtduncan !