Sway provides the workspace "num" property which is an integer number of
the workspace, i.e., workspace "3" -> 3 and also "3dev" -> "3". This
commit uses this property to sort the workspaces, which makes sense when
persistent workspaces or all-output is specified. This commit also adds
a new configuration option, whether the numeric workspaces come in front
or after workspaces that have non-numeric name.
6fe764540c