add constant support
add constant support

esteve/rosidl_typesupport,esteve/rosidl_typesupport,ros2/rosidl,ros2/rosidl_typesupport,ros2/rosidl_typesupport,ros2/rosidl,esteve/rosidl,esteve/rosidl,ros2/rosidl,esteve/rosidl,esteve/rosidl_typesupport,ros2/rosidl,ros2/rosidl_typesupport