How to work with private repositories?

The pipeline works fine but when I add the repo and try to use it, I get the following error:

```
Error: Failed to fetch https://github.com/{{org}}/{{repo}}/releases/download/{{version}}/{{version}}.tgz : 404 Not Found
```
I believe that is happening because helm can't authenticate.
I already tried to add the repository using my username and personal access token but it's not working.

That's how I added the repo:

```
helm repo add --username {{username}} --password {{personal_token}} {{org}} https://{{org}}.github.io/{{repo}}
```

Someone knows if does exists some trick to use it with private repos?

Start by tracing how the pipeline invokes Helm and how the shown `helm repo add` credentials relate to the GitHub Releases URL. Determine whether private repositories are supported by the action; done should be a documented or implemented way to authenticate and fetch a private chart repository successfully.

Written by the indexing model from the issue text.