Added Exploring Modern Fortran Basics (#6449)

* Added Exploring Modern Fortran Basics

Hi,

Stjepan from Manning here. I thought this title might be a good match for your list. Thank you for considering it.

Best,

* Added Exploring Math for Programmers...

Hi, 

Stjepan from Manning here. I thought this title might be a good match for your list. Thank you for considering it.

Best,

* address linter issues
Co-authored-by: NEric Hellman <eric@hellman.net>

books/free-programming-books-langs.md

@@ -763,6 +763,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 ### Fortran
 
+* [Exploring Modern Fortran Basics](https://www.manning.com/books/exploring-modern-fortran-basics) - Milan Curcic
 * [Fortran 90 Tutorial](http://www.cs.mtu.edu/~shene/COURSES/cs201/NOTES/fortran.html) - C.-K. Shene at Michigan Technological University (HTML)
 * [Fortran 90 Tutorial](https://web.stanford.edu/class/me200c/tutorial_90/) - Sarah T. Whitlock, Paul H. Hargrove at Stanford University (HTML)
 * [Fortran information & resources](https://www.fortranplus.co.uk/fortran-information/) - fortranplus.co.uk (HTML)

books/free-programming-books-subjects.md

@@ -489,6 +489,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 
 * [A Mathematical Theory of Communication](https://archive.org/details/bstj27-4-623) - Claude E.Shannon
 * [Discrete Structures for Computer Science: Counting, Recursion, and Probability](http://cglab.ca/~michiel/DiscreteStructures/) - Michiel Smid
+* [Exploring Math for Programmers and Data Scientists](https://freecontent.manning.com/free-ebook-exploring-math-for-programmers-and-data-scientists/) - Paul Orland
 
 
 ### Misc