Also auto_tile on Focus events

Actually, I'd rather wish there was a Resize event so that one could auto_tile
after resizes (a window might become to small for splith or wide enough for
splith) but there is no such event.  So by switching focus back and forth, one
can have the same effect.

src/demon.rs

@@ -121,6 +121,7 @@ fn handle_window_event(
     } = *ev;
     match change {
         s::WindowChange::Focus => {
+            maybe_auto_tile(layout);
             update_last_focus_time(container.id, extra_props);
             println!("Handled window event type {:?}", change);
             true