[0.19.0] Instance blocking

[mormaer]

Introduction

As discussed in the recent Lemmy announcement users will now have the ability to block instances.

Users can now block instances, so that their communities are hidden from listings. This is done via POST /api/v3/site/block with parameters int instance_id, bool block.

LemmyNet/lemmy#3869

Requirements

We should add support for this as soon as possible, the option would need to be gated behind a version check as it will not be available below 0.19.0.

[Sjmarf]

Another way to arbitrarily block an instance may be to use the load settings from json endpoint, which allows you to specify instance domains.