unsupported media type application/vnd.devcontainers when pulling template image

Hello.

I have created my own devcontainers template repository (https://github.com/brpaz/devcontainer-templates) using the [template-starter](https://github.com/devcontainers/template-starter), but I when I try to use my template as a base image in another project, I got the following error:

```
[2650 ms] Start: Run: docker pull ghcr.io/brpaz/devcontainer-templates/nix-devenv:latest
latest: Pulling from brpaz/devcontainer-templates/nix-devenv
unsupported media type application/vnd.devcontainers
[3888 ms] []
[3888 ms] Error: No such image: ghcr.io/brpaz/devcontainer-templates/nix-devenv:latest
```

The image exists in the repository. Probably something very dumb, but I can´t see what I am missing.

Any help is appreciated.