Show headers in examples

[martinthomson]

The examples show compact JWT and CWT text and payloads, but none show the header. The header is the most interesting part in some ways.

[decentralgabe]

@martinthomson I believe the CWT headers are present in the diagnostic notation? https://w3c.github.io/vc-jose-cose/#securing-json-ld-verifiable-credentials-with-cose

for JWT/SD-JWT I agree it would be nice to show the headers, I can make that update.