Confirm accuracy of JSON interfaces in light of recent spec PR's

[MasterKale]

Describe the issue

There have been some recent clarifications made to the various JSON serialization-related structs added to L3 of the spec. Make sure this library is still accurate as platform and browser vendors start to return these in the wild:

• Mark all JSON fields as required. w3c/webauthn#1878
• Include the "Easily accessing credential data" fields in JSON. w3c/webauthn#1887

[MasterKale]

Types are mostly fine, but I need to add some values to AuthenticatorAttestationResponseJSON. PR #400 will take care of these updates.