[charms] Proposing Rodrigo Barbieri for OpenStack Charms stable core

Hi everyone, I'd like to propose Rodrigo Barbieri for the OpenStack Charms stable maintenance team. Rodrigo has been a contributor to the charms for many years and has an impressive history of contributions to across all the OpenStack charms. He always demonstrates an attention to detail and provides insightful feedback in reviews and as such I believe he would make a valuable addition to our charms-stable maintenance core team. Thank you for your contributions to the project Rodrigo! Regards, Ed