[Feature Request] Copying subscriptions to other accounts.

It would be useful to be able to automatically subscribe to all communities that another one of your accounts is subscribed to.

The use case would be, a user originally joined lemmy.world, but the instance is overloaded and the user wishes to migrate to another instance. They could create a new Lemmy account on another instance and press a button to automatically copy all of their subscriptions from their original account to this new account.

It would save the user a tremendous amount of time hunting down all of the communities they were originally subscribed to and honestly make migration nearly painless.

This is kind of a weird advanced request, but I see it having a lot of value with the way Lemmy is setup.