added fullscreen_mode to get_tree output

Signed-off-by: NokiDev <noki.dev@gmail.com>

sway/ipc-json.c

@@ -421,6 +421,7 @@ static void ipc_json_describe_container(struct sway_container *c, json_object *o
 		view_is_urgent(c->view) : container_has_urgent_child(c);
 	json_object_object_add(object, "urgent", json_object_new_boolean(urgent));
 	json_object_object_add(object, "sticky", json_object_new_boolean(c->is_sticky));
+	json_object_object_add(object, "fullscreen_mode", json_object_new_int(c->is_fullscreen));
 
 	struct sway_node *parent = node_get_parent(&c->node);
 	struct wlr_box parent_box = {0, 0, 0, 0};