docs: add window_type to ipc documentation
docs: add window_type to ipc documentation

Airblader/i3,Airblader/i3-original,i3/i3,Airblader/i3,stapelberg/i3,Airblader/i3,Airblader/i3,i3/i3,Airblader/i3-original,i3/i3,i3/i3,Airblader/i3-original,stapelberg/i3,stapelberg/i3,Airblader/i3-original,stapelberg/i3,Airblader/i3-original