Add a reference to the new source entry requirement for ros2-gbp repo…

…sitory creation. (#2992) (#3012)

* Add a reference to the new source entry requirement for ros2-gbp repository creation.

As discussed, we're adding a requirement to the release repository
creation process to add a source stanza, ensuring that the packages in
the new repository undergo rosdistro review before a release repository
is created. This is particularly important for naming convention review
since that review could affect the name of the source, and by extension,
release repository created.

Co-authored-by: Chris Lalancette <clalancette@openrobotics.org>
(cherry picked from commit ecdfd5f)

Co-authored-by: Steven! Ragnarök <nuclearsandwich@users.noreply.github.com>

source/How-To-Guides/Releasing/Release-Team-Repository.rst

@@ -61,7 +61,9 @@ Having a release repository separate from your source code repository is a requi
 Create a new release repository
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Fill the `Add New Release Repositories issue <https://github.com/ros2-gbp/ros2-gbp-github-org/issues/new?assignees=&labels=&template=new_release_repository.md&title=Add+new+release+repositories>`_ issue template
+If your repository is new to the ROS community, you should first open a pull request on `ros/rosdistro <https://github.com/ros/rosdistro>`_ adding a ``source`` entry for your repository.
+The review process for the rosdistro database will ensure your repository and packages conform to the `REP 144 package naming conventions <https://www.ros.org/reps/rep-0144.html>`_ and other requirements before release.
+Once your package name has been approved and merged, fill in the `Add New Release Repositories issue <https://github.com/ros2-gbp/ros2-gbp-github-org/issues/new?assignees=&labels=&template=new_release_repository.md&title=Add+new+release+repositories>`_ issue template
 if you don't have a release repo for your project yet.
 
 What if my existing release repo isn't on ros2-gbp?