XEP-0231: Bits of Binary - for custom smileys and CAPTCHA

[schoerg]

Is your feature request related to a problem? Please describe.

XEP-0231 is used to transfer small bits of binary, hence the name between clients. In Pidgin it is used to transfer custom smileys. Those are limited to 8KiB as per the XEP.

Also some MUCs sent CAPTCHA pictures via this XEP. Gajim does support XEP-0231 for CAPTCHAs. Issue #1092 also mentions XEP-0231 in its XEP spec.

Describe the solution you'd like
Implement at least receiving custom pictures, if possible also sending custom ones.

Describe alternatives you've considered
Maybe Stickers, but unsure if those are always a sperate message. BOB pictures can usually be inlined.

Additional context
https://xmpp.org/extensions/xep-0231.html

Example picture from Pidgin: