[Gtk4] Treeexpander don't add extra indent if no expander is shown
I would very much welcome an option for GtkTreeExpander to not add an additional indent block in front of the child when no expander is shown.
My use-case is almost exclusively rows with an expander at the top-level of the list and rows without an expander as their children. The extra indent block makes this look a bit off.
If an additional property like this for GtkTreeExpander is an idea that is welcome I would like to prepare a merge request.