mrnemesys EDIT: rephrased my comment
Are you publishing this as an intended Pull Request or as an advice for other users of the extension ?
I won't be adding any translation to this extension, so it would be best for you to directly submit as a PR it to a language pack.
As for people who might want to use this directly, I strongly recommend not touching anything in
vendor folder as it's managed by Composer. Instead the translations should either be added to a fork or development copy of the extension (workbench folder), to a language pack, registered via
extend.php or added via Linguist (not an option with b9 for now).