Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `README.md`:
  Upstream changed their README, we have our own.
  Kept ours.
- `app/helpers/application_helper.rb`:
  Minor code style fix upstream, on a line that is different in glitch-soc
  due to the different theming system.
  Applied the code style fix to our own code.
- `app/views/settings/preferences/appearance/show.html.haml`:
  Code style fix on a line next to lines exclusive to glitch-soc.
  Applied upstream changes.
- `yarn.lock`:
  Upstream updated a dependency textually close to a glitch-soc-only
  dependency.
  Updated the dependency like upstream did.

spec/presenters/instance_presenter_spec.rb

@@ -3,7 +3,7 @@
 require 'rails_helper'
 
 describe InstancePresenter do
-  let(:instance_presenter) { InstancePresenter.new }
+  let(:instance_presenter) { described_class.new }
 
   describe '#description' do
     around do |example|