[Feature request] Handle bottom panel

[Thesola10]

I want to use Dash to Panel with PaperWM, and so far it works just fine (well, it would if GNOME 40 hadn't broken everything :p) with one caveat: PaperWM still assumes that the panel is on top, and forces a good amount of wasted space above the windows to leave room for a nonexistent panel.

Would it be possible to detect the panel edge and update margins to fit, or at least allow the user to punch in negative values for the top margin?