Add SELinux Notebook to Security and Linux sections (EbookFoundation#12000)

* Add SELinux Notebook to Security and Linux sections
- Added The SELinux Notebook to free-programming-books-subjects.md under Security with a single link.

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

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

---------

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

Author: pranlawate

books/free-programming-books-subjects.md

@@ -887,6 +887,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Security Engineering](https://www.cl.cam.ac.uk/~rja14/book.html)
 * [The Joy of Cryptography (2021)](https://joyofcryptography.com/pdf/book.pdf) - Mike Rosulek (PDF)
 * [The MoonMath Manual to zk-SNARKs](https://leastauthority.com/community-matters/moonmath-manual/) - Least Authority
+* [The SELinux Notebook](https://github.com/SELinuxProject/selinux-notebook) - Richard Haines, Paul Moore, SELinux Community (HTML, PDF, EPUB, azw3) (GFDL)
 
 
 ### Software Architecture