[feature request] Direct switch to workspace up or down on mouse wheel action

[Etienne-TR]

It would be very convenient to be able to switch directly from one workspace to another by using the mouse wheel hover the workspace launcher applet, as is already the case with the numbered workspaces applet.

This would provide this functionality without having to display the numbered workspaces applet, or simply increases the chance of having it near your cursor by adding an area where it can be used.