Update example script (or add a new one) that issues a version 2 credential

[dlongley]

This example script could perhaps be modified to demonstrate the issue: https://github.com/digitalbazaar/vc/blob/main/examples/rt.js

We should ensure we update that script (or add another) to show a v2 VC anyway -- so I'll file an issue for that.

Originally posted by @dlongley in #197