Include changelog in Helm chart

[lindhe]

Today, this repo produces two types of releases: one for the binary and one for the Helm chart. That is fine, but the Helm chart has almost no info attached to it so it is hard to identify what changes have been made between versions.

Instead, what I typically do, is to first checkout the Helm chart and identify the appVersion for that Helm chart version and then go to that release on GitHub and read the changelogs.

I think it would be a big improvement if changelogs were included in the Helm chart! Either by attaching the same information to the Helm chart release as the binary release, or by attaching a CHANGELOG.md file in the actual Helm chart (like Bitnami often does for other Helm charts), or both!

This should, I hope, also make it easier for third party tools like Renovate to automatically detect the changelog.