[FEATURE] Support Webauthn/FIDO2 passkey logins

[jhsul]

It would be very awesome if tinyauth supported passkey logins, and I would happily toss a few bucks toward the GitHub sponsorship if anyone is willing to put some time into implementing this :)

Thanks for the cool project!

[steveiliop56]

Hello!

Passkeys are quite complex and they require a database to function, that's why I would recommend using pocket ID for passkeys and then using it as an OAuth provider for tinyauth (OIDC is built on top of OAuth so pocket ID will work perfectly). So, currently it's not really possible to implement passkey support unless I change tinyauth in the future and add a state. In any case thank you for the suggestion and the nice words!