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.

.github/workflows/build-image.yml

@@ -49,7 +49,7 @@ jobs:
           platforms: linux/amd64,linux/arm64
           provenance: false
           builder: ${{ steps.buildx.outputs.name }}
-          push: ${{ github.event_name != 'pull_request' }}
+          push: ${{ github.repository == 'mastodon/mastodon' && github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha