Allow local authentication for devices without biometrics.

Ideally, a method (LocalAuthentication().authenticate()) that would defer to the OS to determine the proper authentication type.

iOS:
https://developer.apple.com/documentation/localauthentication/lapolicy/lapolicydeviceownerauthentication?language=objc

Android:
https://developer.android.com/training/sign-in/biometric-auth#biometric-or-lock-screen