move workspace/desktop from WSSwitcher=>Pager
pass Workspace instead of [Workspace] and index to mark/markImg
rename mark => markWs
move markWs/markImg from WSSwitcher=>Pager
dont apply the 'hidden' markup styling initially, just set the name
expose workspace-update IO actions, instead of just label markup

e.g.:
activeWorkspace = colorize "white" "black"
=>
activeWorkspace = markWs $ colorize "white" "black"
fix a bug in hideEmptyWs=True where workspace show/hide would occasionally crash

it was happening outside of gtk main thread, and prone to race conditions