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

Conflicts:
- `CHANGELOG.md`:
  Upstream added newlines.
  Conflicts are because the CHANGELOG was independently merged from 3.4.6 on
  last security update.
  Took upstream's version.
- `app/helpers/context_helper.rb`:
  Conflicts because of extra vocabulary in glitch-soc. The conflicts were
  actually handled in last security merge.
  Kept our version.

.github/workflows/build-image.yml

@@ -11,6 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: docker/setup-qemu-action@v1
       - uses: docker/setup-buildx-action@v1
       - uses: docker/login-action@v1
         with:
@@ -29,6 +30,7 @@ jobs:
       - uses: docker/build-push-action@v2
         with:
           context: .
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/mastodon:latest