ci: optimize CI/CD pipeline with Docker build cache

- Add Docker build cache configuration to GitHub Actions workflow

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

.github/workflows/docker.yml

@@ -70,3 +70,5 @@ jobs:
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.docker-meta.outputs.tags }}
           labels: ${{ steps.docker-meta.outputs.labels }}
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}:buildcache
+          cache-to: type=registry,ref=ghcr.io/${{ github.repository }}:buildcache,mode=max