Add Scikit Learn Choosing the Right Estimators cheatsheet (#11583)

* Add Scikit Learn Choosing the Right Estimators cheatsheet

* Remove scikit learn cheat sheet

* Remove an extra space at end of section

* Add Scikit Learn user guide

* Change title of scikit learn user guide and move it downwards

* Remove period from scikit-learn user guide entry

Co-authored-by: Eric Hellman <eric@hellman.net>

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Co-authored-by: Eric Hellman <eric@hellman.net>

books/free-programming-books-subjects.md

@@ -453,6 +453,7 @@ Books that cover a specific programming language can be found in the [BY PROGRAM
 * [The Python Game Book](https://web.archive.org/web/20210308080726/https://thepythongamebook.com/en%3Astart) - Horst Jens *(:card_file_box: archived)*
 * [Top 10 Machine Learning Algorithms Every Engineer Should Know](https://www.dezyre.com/article/top-10-machine-learning-algorithms/202) - Binny Mathews, Omair Aasim
 * [Understanding Machine Learning: From Theory to Algorithms](https://www.cs.huji.ac.il/~shais/UnderstandingMachineLearning) - Shai Shalev-Shwartz, Shai Ben-David
+* [User Guide - scikit-learn](https://scikit-learn.org/stable/user_guide.html) - Scikit-learn developers (HTML) (BSD)
 
 
 ### Mathematics