Key64 should be an array of 64 32 byte keys 
Hi, I'm working on a fork of this project and noticed that deserialization/ serialization of RCT types 1 and 2 fail. I found the issue it's because [key64 in this library](https://docs.rs/monero/0.16.0/src/monero/util/ringct.rs.html#80) is a 64 byte key whereas in the [Monero library](https://github.com/monero-project/monero/blob/9750e1fa103539b3e533455500610aae76e253a5/src/ringct/rctTypes.h#L145) it's an array of 64 32 byte keys 

[example RCT type 1](https://xmrchain.net/tx/3a5c20de26fc2a8c6ca68ab8facdb58c91da711b4f0e2f79e29d8e0270ade33d/1)
[example RCT type 2](https://xmrchain.net/tx/4a5fd752ebb0bb9bc6c82ad0b9bf1d0df02401aeb1c6cecbffd506902636cd7f)

