Optionally send fake credentials to Responder

[lawndoc]

I was recently made aware of another project that is similar to this one: Ben0xA/HoneyCreds

I really like HoneyCreds' strategy of going a step further and sending fake credentials to Responder. If we see the honey creds used on a different host than Responder, it could reveal additional compromised endpoints under the attacker's control.

I'd like to implement a similar feature into Respotter that allows for fake credentials to be sent if a username is configured. If the credential configuration is empty, then Respotter will not send any credentials.