Helm chart repo is offline

Per your docs at https://charts.ntppool.org/, adding the chart repo does not work.  Has the repo moved or when can it be expected to be back online?

```
€ helm repo add ntppool https://charts.ntppool.org/
Error: looks like "https://charts.ntppool.org/" is not a valid chart repository or cannot be reached: failed to fetch https://charts.ntppool.org/index.yaml : 403 Forbidden
```