Add Artifacthub changelog annotations

[lusu007]

Is your feature request related to a problem?

Chart changelogs are not displayed on Artifacthub.com

Helm chart

All

Desired feature

Add Artifacthub's changelog annotation.

see: https://blog.artifacthub.io/blog/changelogs/

Considered Alternatives

N/A

Additional Context

N/A

[meyfa]

Related to #27

If we go through the effort of manually creating changelog entries anyway, we might as well add them to a markdown file, too. WDYT?

Or perhaps we make a pre-commit hook to generate one from the other.