Offers sticky groups for i3.
Sticky groups are a concept wherein you have multiple containers on different
workspaces that belong to the same »sticky group.« Most of these windows will
be simple placeholders as they won't be visible, but only one window will be
the actual window to display. Whenever you switch workspaces, i3-sticky will
swap the designated window into the placeholder on the new workspace if such a
container is present. This allows you to have a sticky tiling window, i.e., a
window that is present on multiple workspaces. Note that for floating windows
you can use the i3 command sticky.
This is a work in progress.
TODO.