Fix chart versioning based on tag events and release YAML assets

[chomatdam]

Current

• Chart version (template) and app versions (nidhogg) are maintained manually
• Kustomize is using newTag and gets Renovate PRs to update that value as well
• Versioning/Releasing is challenging because of the cyclic dependency between 3rd parties and nidhogg

Desired

• Set Chart.yaml version to a placeholder version 0.0.0 (with comment) so that we can still helm install/package locally
• Defer responsibility of tagging the Chart.yaml version to the CI workflow when releasing a new version
• Publish YAML artifact asset based of helm template when releasing a new version that can be consumed by 3rd parties
• kustomize folder is removed and replaced by an example of custom config in the documentation directly
• README.md is streamlined and indicating where to find the latest chart release in GitHub packages