Can't convert stunner-gateway-operator on github...  gzip:invalid header

Hi, what's the best way to convert this helm chart?  Thank you!

```
> $ docker run -ti containersol/helm-convert convert https://github.com/l7mp/stunner-helm/tree/main/helm/stunner-gateway-operator
Error: gzip: invalid header
Usage:
  convert [flag] [chart URL | repo/chartname] [...] [flags]

Examples:
...
```
