Update free-science-books.md

[jyoti-bhogal]

Added the link to the book Elements of Statistical Learning

What does this PR do?

Add Resource(s) | Remove Resource(s) | Add info | Improve Repo Added link to a book

For resources

Description

Why is this valuable (or not)

It is a good read to understand the statistical concepts for data analysis.

How do we know it's really free?

It is available on the official website

For book lists, is it a book?

Yes, it is a book

Checklist:

• [x] Not a duplicate
• [x] Included author(s) if appropriate
• [x] Lists are in alphabetical order
• [x] Needed indications added (PDF, access notes, under construction)

[jyoti-bhogal]

Will create a proper PR. Hence closing this PR.