Merge #1887 into main

[MasterKale]

I didn't catch before merging it that #1887 sought to merge a "jsoneasy" branch into a "json" branch. I think it was intended to target "main" branch, though, so I went ahead and did that here.

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[emlun]

I'll take the opportunity to tag this for inclusion in this PR too: #1887 (comment)

I realize belatedly that we probably also need instructions on how to populate these new fields, like we have for clientExtensionResults and transports:

webauthn/index.bs

Lines 1592 to 1602 in 6dfbdba

	The
	{{RegistrationResponseJSON/clientExtensionResults|RegistrationResponseJSON.clientExtensionResults}} or
	{{AuthenticationResponseJSON/clientExtensionResults|AuthenticationResponseJSON.clientExtensionResults}}
	member MUST be set to the output of {{PublicKeyCredential/getClientExtensionResults()}},
	with any {{ArrayBuffer}} values encoded to {{DOMString}} values using
	[=base64url encoding=]. This MAY include {{ArrayBuffer}} values from extensions registered
	in the IANA "WebAuthn Extension Identifiers" registry [[!IANA-WebAuthn-Registries]] but not
	defined in [[#sctn-extensions]].
	The {{AuthenticatorAttestationResponseJSON/transports|AuthenticatorAttestationResponseJSON.transports}}
	member MUST be set to the output of {{AuthenticatorAttestationResponse/getTransports()}}.

I'll open a follow-up PR.

I can draft the proposed change.

[emlun]

Requesting @agl to review commit fe4d21f6cf374c2a6d726d1e0644c10acbf3e06d in particular.

[agl]

Thank you for catching that.