kevins38507913 - I don't think, it's officially supported but you can try adding the new language node at /etc/social/config/languageOpts/languageMapping(refer other language nodes on how to create one). That being said, even if this works, I see a practical roadblock in the actual functionality - AEM Internationalization may not contain translations for site's navigation strings as well the OOTB strings used in communities site for the new language(It's important to make sure that semantic meaning is preserved).
So, if you really need to add a new language, I would recommend opening a daycare ticket, to check if your language is supported by AEM internationalization or if it can be added.