Ensure codec values are registered in the spec.

[davidlehn]

This value is used here but not registered in the spec:

_addRegistration(0x32, 'https://purl.imsglobal.org/spec/ob/v3p0/context.json');

If the id is stable enough to last forever, it should be registered in the spec. If not, then this lib and the spec needs a new feature to support use of unregistered ids.

[davidlehn]

This context may already be obsolete.
See:
json-ld/cbor-ld-spec#15

[BigBlueHat]

This implementation is being used to inform a new updated CBOR-LD spec at https://github.com/json-ld/cbor-ld-spec/

Consequently, we'll need to make some decisions on how we handle OpenBadges context file proliferation.