ci: enhance Docker workflow with ARM64 support and caching

- Add support for `linux/arm64` platform in Docker workflow
- Enable build cache from and to registry in Docker workflow

Signed-off-by: appleboy <appleboy.tw@gmail.com>

.gitea/workflows/docker.yml

@@ -90,10 +90,12 @@ jobs:
           ACTIONS_RUNTIME_TOKEN: ""
         with:
           context: .
-          platforms: linux/amd64
+          platforms: linux/amd64, linux/arm64
           file: docker/Dockerfile
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.docker-meta.outputs.tags }}
           labels: ${{ steps.docker-meta.outputs.labels }}
           provenance: false
           sbom: false
+          cache-from: type=registry,ref=gitea/example-go:buildcache
+          cache-to: type=registry,ref=gitea/example-go:buildcache,mode=max