Add web design book (#5779)

* feat: add Web Design Primer book

* feat: change order

* feat: change category
Co-authored-by: NAlexandre VU <alexandre.vu@montreal.ca>

books/free-programming-books-subjects.md

@@ -262,6 +262,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 * [Programming with gtkmm 4](https://developer.gnome.org/gtkmm-tutorial/stable/)
 * [Search User Interfaces](http://searchuserinterfaces.com/book/) - Marti A. Hearst
 * [The GLib/GTK+ Development Platform](https://people.gnome.org/~swilmet/glib-gtk-dev-platform.pdf) - Sébastien Wilmet (PDF)
+* [Web Design Primer](https://pressbooks.library.ryerson.ca/webdesign/) - Richard Adams, Ahmed Sagarwala
 
 
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