Specify missing implementation for webauthn "direct" and "enterprise" attestation options

[taraldr]

Summary

Firefox on mobile does not support the "direct" or "enterprise" options for credentialCreationData.attestationConveyancePreferenceOption. This PR updates the data to reflect this.

Supporting details

Here's the issue which explains that firefox on mobile has not yet implemented a dialog which would satisfy their self-imposed privacy requirement for direct attestations, and therefore do not currently support a "direct" or "enterprise" attestation option: https://bugzilla.mozilla.org/show_bug.cgi?id=1550164

[queengooborg]

Hey there, thank you for your PR and welcome to BCD!

This information should be added as subfeatures, rather than as a note with partial implementation. Would you be down to update the PR accordingly?

[caugner]

This information should be added as subfeatures, rather than as a note with partial implementation. Would you be down to update the PR accordingly?

@queengooborg Since attestation is an option on the publicKey option (according to this example), should this be a note and partial implementation of the publicKey option, or would you prefer this to really be a sub-feature of the publicKey_option? Technically, the individual values (direct, enterprise) could be considered sub-features of the attestation option, but this is a lot of overhead for documenting this.