Vocabulary languages misses a lot entries
Currently, the vocabulary iso-639-3 (languages) only have some items available (https://sshoc-marketplace-api.acdh-dev.oeaw.ac.at/api/vocabularies/iso-639-3). There should be a lot more of them, especially we are currently in need of "mul" (multiple) and "spa" (spanish), as they are used by the curated items. Can we extend the vocabulary at least with this two terms and in the long term, we should have a more exhaustive list e.g. https://en.wikipedia.org/wiki/Wikipedia:WikiProject_Languages/List_of_ISO_639-3_language_codes_(2019)