Add Security Considerations related to advances in Artificial Intelligence

[msporny]

I've been having a set of discussions with leading researchers in the field of artificial intelligence and challenges that will be created as capabilities in that field advance. Even today, arguably, artificial intelligence "passes" traditional and more modern Turing tests, with humans being unable to tell the difference between an AI and a human when interacting with each other through a text-based medium. This has implications on verifiable credentials, where AIs will be able to legitimately acquire and utilize the same verifiable credentials that humans do. There is a growing desire to understand when a human is at the other end of a transaction on the Web, and when that actor might be an AI. The Security Considerations in the specification should mention something about advanced AI, its use of verifiable credentials, and how that might change the security posture of a system.