enable export & import

[dongzhuoer]

When user resintall system, etc, it would be awesome if he can export all Sets into a .json file and import them back. It is even greater if enables synchronizing with Google account

[jmhobbs]

That's a good idea! I'll try to get back into developing on this unless you'd like to contribute it 😄

[dongzhuoer]

Thank you, but I haven't developed Chrome extension before.