(REVISED) add free online book on Differential Privacy, in security & privacy section (#9191)

* add free online book on Differential Privacy

* add free online book on Differential Privacy

* security and privacy section

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

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

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

books/free-programming-books-subjects.md

@@ -42,7 +42,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 * [Regular Expressions](#regular-expressions)
 * [Reverse Engineering](#reverse-engineering)
 * [Search Engines](#search-engines)
-* [Security](#security)
+* [Security & Privacy](#security--privacy)
 * [Software Architecture](#software-architecture)
 * [Standards](#standards)
 * [Theoretical Computer Science](#theoretical-computer-science)
@@ -771,7 +771,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Solr for newbies workshop (2019)](https://github.com/hectorcorrea/solr-for-newbies) - Hector Correa ([PDF](https://github.com/hectorcorrea/solr-for-newbies/blob/master/tutorial.pdf))
 
 
-### Security
+### Security & Privacy
 
 * [A Graduate Course in Applied Cryptography](http://toc.cryptobook.us)
 * [Crypto 101 - Crypto for everyone](https://www.crypto101.io)
@@ -787,6 +787,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [OWASP Testing Guide 4.2](https://owasp.org/www-project-web-security-testing-guide/v42/) - The OWASP® Foundation (HTML, [PDF](https://github.com/OWASP/wstg/releases/download/v4.2/wstg-v4.2.pdf))
 * [OWASP Top 10 for .NET Developers](http://www.troyhunt.com/2011/12/free-ebook-owasp-top-10-for-net.html)
 * [Practical Cryptography for Developer](https://cryptobook.nakov.com) - Svetlin Nakov (GitBook) (:construction: *in process*)
+* [Programming Differential Privacy](https://programming-dp.com) - Joseph Near, Chiké Abuah (HTML, PDF)
 * [Security Engineering](http://www.cl.cam.ac.uk/~rja14/book.html)
 * [The Joy of Cryptography (2021)](https://joyofcryptography.com/pdf/book.pdf) - Mike Rosulek (PDF)