Add shortcuts for tiling to quarters

Submitted by a-r..@..gmx.de

Assigned to Xfce Bug Triage

Link to original bug (#11636)

Description

There are already shortcuts for tiling to the left/right/up/down. Xfce 4.12 introduced tiling to quarters. It would be greate to assign custom shortcuts for that as well.

Version: 4.12.1