The panel-button introduces some horizontal padding which is insensitive to scroll events. Without this change, there is a small dead zone in the corner that cannot be used to switch workspaces with the mouse wheel. For useMenu mode, this has the effect of removing all of the horizontal space to the edge of the screen, so I add some back with the status-label-bin margin. This a is similar change to8bad8a3b63. Fixes #315. Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/171> (cherry picked from commitd6648b0b5c)