Don't use Google Charts

[tianhuil]

Hi,

I love that you are building node-2fa. Could we please remove the qr code using Google Charts? That has your entire secret, and you don't want to publish to Google. Instead, you can use QR as a data URL and only display it to the user: https://github.com/speakeasyjs/speakeasy#displaying-a-qr-code.

[satyavh]

The implementation of Google charts in this package is deprecated, shouldn't be used anymore