Add more examples

[hannestschofenig]

Adding more examples to cover other algorithms and the use of HPKE for establishing a secret with COSE_Mac would be good.

[OR13]

https://www.rfc-editor.org/rfc/rfc7520

It would be extra cool, if we could give COSE and JOSE test cases for the same key pairs, represented in COSE Key and JWK