Implement FIDO2 WebAuthn

[olemis]

Feature description

FIDO2 WebAuthn support

Describe the solution you'd like
Incorporate FIDO2 Web Authentication (WebAuthn) and Client-to-Authenticator Protocol (CTAP) specifications to enable secure login authentification.

Additional context
FIDO2 is a joint initiative of FIDO alliance and World Wide Web Consortium’s (W3C). Expanding on Universal Authentication Framework (UAF) and Universal Second Factor (U2F), FIDO2 aspires to enable access to online services completely without the need of user-generated passwords.

See also FIDO2 Credentials, FIDO feature page, and a blog article.

Requires fibercrypto/skywallet-protob#78

Possible implementation

• Implement WebAuthnListResidentCredentials message handler
• Implement WebAuthnAddResidentCredential message handler
• Implement WebAuthnRemoveResidentCredential message handler
• Implement WebAuthnCredentials message handler