FR: Add support for Oprf RISTRETTO255_SHA512 in opaque.

[angelsenra]

https://github.com/cloudflare/voprf-ts seems to have evolved quite a bit since the last release that this code depends on. On new versions, r255 was added. This would make this library compatible (with serialization differences) with libopaque among others.

Please consider updating the oprf library version and thus enabling support for 255. Thanks!

[armfazh]

Lately I'm working on updating the libraries. So this feature will land at a near point the future.

[brobin002]

Hello!

Any news or plan to support RISTRETTO255_SHA512?

Thanks a lot for your work!!