[Engine request] Kheina

[martinezjason]

Is your feature request related to a problem? Please describe.
kheina.com is a search engine similar to iqdb, except specialized in indexing artworks posted on furaffinity.

Describe the solution you'd like
Their URL search template is https://kheina.com/?url=%s (Although it seems to be broken right now?)
Search by image is done through form-data.

Describe alternatives you've considered
It might be supersetted by SauceNao, which, indexes FA "every few hours" according to their status page.
Their index might be slightly (insignificantly) fresher, though, since they claim to update it every 15 minutes. Plus, they might have more accurate results for that particular site due to specialization?
Either way, it might be worth looking into.