Support accounting for reserved/exclusive area in size/move window rules

[skissue]

Description

Currently, the size and move window rules work with respect to the entire monitor size; e.g. a window rule of size 100% 20% will create a window that spans the entire width of the monitor.

Could there be an option to account for reserved area? I'd like to have a window rule that spans the width of my screen, but exclude the area that my vertical bar uses on the left of my monitor.