Add an easy method of transferring user data to another device

[Geo25rey]

Problem

It is unlikely that users have only one device these days, so making a secure method of sharing user data to a new device would be wise. Currently, user data can be manually imported by copying the user data directory from one device to another, but that can be hard for non-technical users and can be impossible on mobile phones.

Potential Solutions

• Have QR code sign-in (like Discord)
• Use Multicast DNS to help share data over a local network