view: add new container as a sibling of tiled view
view: add new container as a sibling of tiled view

If the focused container is floating by itself, create a new container
in tiling mode as a sibling of the inactive focused container instead of
creating it as a sibling of everything that is in tiling mode in that
workspace. This is the i3 behavior.

1ace/sway,1ace/sway,1ace/sway