readme: add a link to gtk4 book
@@ -11,7 +11,7 @@ Currently, the minimum supported Rust version is `1.51.0`.
## Documentation
- The Rust API [Stable](https://gtk-rs.org/gtk4-rs/stable/latest/docs/gtk4)/[Development](https://gtk-rs.org/gtk4-rs/git/docs/gtk4/)
-- Book [Stable]/[Development](https://gtk-rs.org/gtk4-rs/git/book)
+- Book [Stable](https://gtk-rs.org/gtk4-rs/stable/latest/book)/[Development](https://gtk-rs.org/gtk4-rs/git/book)
- [Examples](https://github.com/gtk-rs/gtk4-rs/tree/master/examples)
- [The C API](https://docs.gtk.org/gtk4/)
- [GTK Installation Instructions](https://www.gtk.org/docs/installations/)
