Allow using passkeys saved in password manager to sign in on desktop

[FineFindus]

[Firefox accounts](https://accounts.firefox.com) allow creating and signing in with passkeys. However, unfortunately the desktop site does not allow users to create/sign-in using a passkey saved in a password manager (e.g. Bitwarden), but doing so is possible on a mobile client. This leads to the bizarre situation, where a passkey created on mobile cannot be used to sign-in on desktop.

Please allow creating/signing in with a passkey saved in a password manager on the desktop site.