Add a helpful utility verify script for developers to customize

[dlongley]

This script should verify a VC or a VP and include sections in the script to add static context URLs and context content, a section to turn on / off an HTTP context loader, a section to customize commonly supported did:key: key types and add them via a did:key driver to the document loader, and a section for adding / removing commonly supported cryptosuites.

A developer should be able to paste a VC or VP to be verified and tweak the boilerplate to customize the document loader for their use case.

We might want this to become a CLI tool in the future, but it may be more valuable (at least in the immediate term) as simple customizable script.