Use a vector instead of a map for for storing the workspace windows.
This orders the windows by the time they were added to the workspace, instead of sorting by address (which is effectively a random order). The new ordering seems to match the wlr/taskbar module
I'd like to ignore some windows from having icons or empty space taken
on the bar. By filtering out empty repr we can supply rewrite rules that
will ignore them from being processed and showing an empty space or
default icon.
