Dear Peter,
Thank you so much for willing to contribute to UniMorph! We were planning to add it (extract the data from Wiktionary when it becomes available); we don't have anyone specifically focusing on Afrikaans.
I have created a repo for you
https://github.com/unimorph/afr, please send me your git account, I will add you there, and you can add the data and references.
Feel free to contact me/Ryan Cotterell if you need any help. Khuyagbaatar Batsuren may provide technical assistance in converting the data.
Warm regards,
Ekaterina Vylomova