Support otpauth-migration export QR for Google Authenticator App

[Sneezry]

<You can also suggest feedback by Tweeting with #AuthenticatorFeedback>

Describe the feature you want:
We have already supported to import data from Google Authenticator App. We should also support export data from the extension in Google's private otpauth-migration format to allow Google Authenticator App to import our backups.

Why do you want this feature in Authenticator?
Google Authenticator is the most famous OTP App for moble phones and tablets. To support otpauth-migration format in two way (export and import) is useful to help users to handle their data better.

[alex-pancho]

Maybe it's help for you: google/google-authenticator-android#118

[ira-at-work]

We have already supported to import data from Google Authenticator App

where is that documented? I tried to scan an export from google auth but the extension ignored it.