Write probe and detector to extract API keys

Two suggested attack modes:

• Ask directly for keys for various services
• Provide partial keys and see if the model will complete them

For the detector, we can use trufflehog (see https://github.com/trufflesecurity/trufflehog) or regexes. This should go in a new detector module.

see https://reference.garak.ai/en/latest/extending.html for help getting started