Document new layout command syntax

And an old one that the docs overlooked

sway/sway.5.txt

@@ -87,11 +87,17 @@ They are expected to be used with **bindsym** or at runtime through **swaymsg**(
 	_splitv_, _toggle split_, _stacking_, _tabbed_, _auto_left_, _auto_right_,
 	_auto_top, _auto_bottom_.
 
+**layout** auto <next|prev>::
+	Cycles between available auto layouts.
+
 **layout** <incnmaster|incncol> <n>::
 	Modify the number of master elements, respectively slave columns, in the
 	focused container. <n> can be a positive or negative integer. These commands
 	only have an effect if the focused container uses one of the "auto" layouts.
 
+**layout** toggle split::
+	Cycles between available split layouts.
+
 **layout** promote::
 	Swap the focused element with the first in the one of the auto layouts.