Include F Sharp for fun and profit

I's an epub version of the site, the author himself links to it

free-programming-books.md

@@ -1015,6 +1015,7 @@
 
 ### F Sharp
 
+* [F# for fun and profit](https://www.gitbook.com/book/swlaschin/fsharpforfunandprofit/details) (ePub)
 * [F# Programming](https://en.wikibooks.org/wiki/F_Sharp_Programming) in Wikibooks
 * [F# Succinctly, SyncFusion](https://www.syncfusion.com/resources/techportal/ebooks/fsharp) (PDF, Kindle) *(Just fill the fields with any values)*
 * [Programming Language Concepts for Software Developers](http://www.itu.dk/courses/BPRD/E2009/plcsd-1-2.pdf) (PDF)