feat: Automatically build helm chart on PR merge

[adberger]

Description

Currently the helm chart version is tied to the application version and thus tied to the application release cycle.
With this PR, a new helm chart gets automatically published if the file Chart.yaml has changed on a PR merge.

Can't be tested in a feature branch, for this reason I can't ensure this works as intended.

Related issues

• Close Split helm chart and application releases #701

Checklist

• I've read the guidelines for contributing to this repository.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[chen-keinan]

@adberger just want to make sure that if appVersion will be updated as well so helm will not be published before new app release and been published , in this case helm install... will fail

[chen-keinan]

@adberger thank you for this contribution.

I have added appVersion change validation.

In case appVersion has been changed the helm release will be triggered manually as before. upon official release cycle