Adopt KeepAChanglog

[pree]

Is your feature request related to a problem? Please describe.
Our CHANGELOG.md is inconsistently formatted across the k8s repos.

Describe the solution you'd like
I've recently stumbled across keepachangelog.com which provides a standard for doing CHANGELOG.md. This is already similar to how we do the CHANGELOG, but has a couple of changes and guidelines.

Additional context
This would also enable us to use a GitHub action to write the CHANGELOG for dependabot changes. An example action I tested would be https://github.com/CramBL/dependabot-changelog-writer

[pree]

What would your thoughts be on this @openbao/openbao-k8s-committers ?

[Nerkho]

Yeah, I like it better than our current one(s).