According to the i3 ipc documentation, `window_rect` excludes the window
decorations from the calculation. This just clarifies that in
`sway-ipc.7.scd`
This add `sway-ipc.7.scd` that documents the IPC protocol.
This also increased the minimum scdoc version from 1.8.1 to 1.9.0 to
allow for table cells to be continued on the following line