Implement automatic passkey enrollment

[alexanderson1993]

https://developer.apple.com/videos/play/wwdc2024/10125/

let capabilities = await PublicKeyCredential.getClientCapabilities();
if (!capabilities.conditionalCreate) { return; }

const options = {
    "publicKey": {
        "rp": { … },
        "user": {
            "name": userInfo.user,
            …
        },
        "challenge": …,
        "pubKeyCredParams": [ … ]
    },
    "mediation": "conditional"
};

await navigator.credentials.create(options);