started out by following this guide: https://www.opcito.com/blogs/creating-helm-repository-using-github-pages
To package a chart use Helm package chart-name
Make first index with Helm repo index --url <github_repository_path> .
Following indexes can be appended to with helm repo index --url <github_repository_path> --merge index.yaml .
Be aware <github_repository_path> should be the URL to the github pages page in this example https://simonstiil.github.io/helm
This was then packaged into a Jenkinsfile to automate the whole process.
From main branch a release is triggered using #release [chart-name] [chart-version]