Added Machine Learning from Scratch (#6359)

* Added Machine Learning from Scratch

* Update books/free-programming-books-subjects.md

Co-authored-by: David Ordás <[email protected]>

* Update free-programming-books-subjects.md

Co-authored-by: David Ordás <[email protected]>

Author: patrick-steve

books/free-programming-books-subjects.md

@@ -329,7 +329,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 * [Learning Deep Architectures for AI](https://mila.quebec/wp-content/uploads/2019/08/TR1312.pdf) (PDF)
 * [Machine Learning](http://www.intechopen.com/books/machine_learning)
 * [Machine Learning for Data Streams](https://moa.cms.waikato.ac.nz/book-html/) - Albert Bifet, Ricard Gavaldà, Geoff Holmes, Bernhard Pfahringer
-* [Machine Learning from Scratch](https://dafriedman97.github.io/mlbook/content/introduction.html) - Danny Friedman
+* [Machine Learning from Scratch](https://dafriedman97.github.io/mlbook/) - Danny Friedman (HTML, PDF, Jupyter Book)
 * [Machine Learning, Neural and Statistical Classification](http://www1.maths.leeds.ac.uk/~charles/statlog/)
 * [Machine Learning with Python](https://www.tutorialspoint.com/machine_learning_with_python) - Tutorials Point (HTML, [PDF](https://www.tutorialspoint.com/machine_learning_with_python/machine_learning_with_python_tutorial.pdf))
 * [Mathematics for Machine Learning](https://gwthomas.github.io/docs/math4ml.pdf) - Garrett Thomas (PDF)