Add missing documentation of automatic_face_movement_max_rotation_per_sec entity parameter

doc/lua_api.txt

@@ -3233,6 +3233,8 @@ Definition tables
         stepheight = 0,
         automatic_face_movement_dir = 0.0,
     --  ^ automatically set yaw to movement direction; offset in degrees; false to disable
+        automatic_face_movement_max_rotation_per_sec = -1,
+    --  ^ limit automatic rotation to this value in degrees per second. values < 0 no limit
         backface_culling = true, -- false to disable backface_culling for model
         nametag = "", -- by default empty, for players their name is shown if empty
         nametag_color = <color>, -- sets color of nametag as ColorSpec