Notify Rolling Maintainers They've Been Automatically Enrolled

[chapulina]

@smac

maintainers of Foxy packages were not notified that their packages are added to rolling

I believe that was explained back when Rolling was created:

@nuclearsandwich

Once Foxy is released, we will “roll” the new rolling release using Foxy as the source.
This means that any maintainer who wants their package to be included in future ROS 2 distributions can target Foxy and as long as their package continues to build as we update the rolling distribution it will be included in future distributions.