ROS2 Package Release Instructions Added!

I recently added the Releasing a Package how-to-guide to the official ROS 2 documentation, which is a port/updated version of the ROS 1 package release guide. It explains more about release tracks and about the new ros2-gbp release repository organization, so check it out even if you have released packages in ROS before!

Link: Releasing a Package — ROS 2 Documentation: Rolling documentation