Add support from authy 2fa windows tool export & firefox tool backup json file

**Describe the feature you want:**
Before this app got developed for firefox, there was only one known 2fa app that worked good.
https://addons.mozilla.org/da/firefox/addon/two-factor-authenticator/

His string goes like this for import / export.

`{"otp_list":[{"name":"Microsoft Dummy Account","key":"XXXXXXX"},{"name":"Google Dummy Account","key":"xxxxxx"}]}`

And for authy try it out your self, this way would go export strings via this tool and import them directly from export line.
https://github.com/alexzorin/authy/releases

**Why do you want this feature in Authenticator?**
Will make it a lot easier and 100% secure and complete without human errors.