Conflicts:
- `app/helpers/application_helper.rb`:
Upstream reworked how CSS classes for the document's body are computed.
Slight conflict due to glitch-soc's different theming system.
Updated as upstream did.
Conflicts:
- `spec/lib/sanitize/config_spec.rb`:
Upstream rewrote top-level `describe` calls to `RSpec.describe`, and
glitch-soc had differences in the first few tests because of the wider
subset of HTML it accepts.
Changed `describe` to `RSpec.describe` as upstream did, keeping
glitch-soc's tests.
