Update Auth with Session Management Scripts Details

[kingthorin]

After 2.10.0 or whatever the next release is.

As discussed:
https://github.com/zaproxy/zap-api-docs/pull/36/files#r422719979

This request is initiated as a client side AJAX request using a spec called JWT. Currently ZAP doesn't have a notion of the Authorization header for sessions so this is where ZAPs scripting engine will come into play! With ZAP's scripting engine, we can easily add to or augment it's functionality.