Add DUO support

[cyber-sec0]

Like https://github.com/FreshSupaSulley/Auto-2FA does

[notoriousdds]

This may or may not interest you.

But... I was able to import my DUO 2FA's to the Authenticator extension using this: https://github.com/notoriousdds/duo-hotp-dosespot

From what I just read about Auto 2FA, it looks like the duo-hotp script is a manual-ish way of doing what Auto 2FA does automatically.

I don't know what can be exported from Auto 2FA (because I've never used it). But, it looks Auto 2FA may also allow you to export the needed secret which could then be imported into Authenticator.

Both methods are hackish, but better than another app for another 2FA IMHO.