Provide passwordless example, or update 1.3.2. to be a passwordless example

[GregBrimble]

Hi, just a suggestion to help clarify the passwordless registration flow for people.

1.3.2. Registration Specifically with User-Verifying Platform Authenticator walks through a process of registering where a user provides a username, password, and uses a user-verifying platform authenticator.

6.2. Authenticator Taxonomy states:

User-verifying platform authenticators and first-factor roaming authenticators enable passwordless multi-factor authentication. In addition to the proof of possession of the credential private key, these authenticators support user verification as a second authentication factor, typically a PIN or biometric recognition. The authenticator can thus act as two kinds of authentication factor, which enables multi-factor authentication while eliminating the need to share a password with the Relying Party.

To me, 1.3.2's example could be improved by not also providing a password, or instead, a new example was created to specifically walk through a passwordless flow.

More than happy to put up a PR to make these changes if you're interested in either. Just let me know!

[timcappalli]

This can be addressed as part of #1720