Check if WebAuthn API available, and if platform authenticator is supported

platformAuthenticatorAvailable.js

const isWebAuthnSupported = () => {
  return !!window.PublicKeyCredential
}

const isPlatformAuthenticatorSupported = () => {
  if (!isWebAuthnSupported()) {
    return Promise.reject(new Error("WebAuthn API is not available"))
  }
  
  if (!PublicKeyCredential.isUserVerifyingPlatformAuthenticatorAvailable) {
    return Promise.resolve(false)
  } else {
    return PublicKeyCredential.isUserVerifyingPlatformAuthenticatorAvailable()
  }
}