[FEATURE REQUEST] Introduce derive macro for ListStore items

[gagath]

Hi,

I am the author of the gtk_liststore_item crate (crates.io, github). I think it would be nice that this macro was introduced inside of the framework instead of requiring to use an external crate for making it less verbose to create and interact with ListStore. Feedbacks on the crate and the possibility to merge are welcome!

[sdroege]

@bilelmoussaoui What do you think? The same would also apply to gtk4, and you probably have an opinion on that :)

[bilelmoussaoui]

@bilelmoussaoui What do you think? The same would also apply to gtk4, and you probably have an opinion on that :)

I don't think such thing would be very useful for gtk4, as most of its new types uses GListModel instead of GtkListStore