wrap workspace's child into a container if needed
wrap workspace's child into a container if needed

If workspace has stacked/tabbed layout, its direct children should be
wrapped into a container which enables them to draw the titlebar.

1ace/sway,sleep-walker/sway,4e554c4c/sway,ascent12/sway,taiyu-len/sway,taiyu-len/sway,SirCmpwn/sway,johalun/sway,ptMuta/sway,1ace/sway,4e554c4c/sway,mikkeloscar/sway,1ace/sway,taiyu-len/sway,sleep-walker/sway,ascent12/sway,mikkeloscar/sway,ascent12/sway