add license to 1 book (#11552)

Co-authored-by: Michelle Paradis <[email protected]>

Author: michpara

Diff for: books/free-programming-books-langs.md

@@ -2634,7 +2634,7 @@ Books on general-purpose programming that don't focus on a specific language are
 
 ### Visual Basic
 
-* [Visual Basic .NET Notes for Professionals](https://goalkicker.com/VisualBasic_NETBook/) - Compiled from StackOverflow Documentation (PDF)
+* [Visual Basic .NET Notes for Professionals](https://goalkicker.com/VisualBasic_NETBook/) - Compiled from StackOverflow Documentation (PDF) (CC BY-SA)
 * [Visual Basic Official Docs](https://docs.microsoft.com/en-us/dotnet/visual-basic)