Allow overriding `app.kubernetes.io/version`

[dominykas]

When image.tag uses a different version of verdaccio than the Chart.yaml, the app.kubernetes.io/version label becomes misleading.

Happy to PR, although haven't had time to think about what would be a good solution to this.

[dominykas]

I think for most people, adding the image.tag into app.kubernetes.io/version when it exists is probably the right thing? i.e. if you're overriding the tag for verdaccio/verdaccio container - that's the "app version" you're running.

It does not quite work for me, because I'm also building my own container, so the version does not match the verdaccio version. But I also do not care about that and the container version is fine for me too. What's an "application version" anyways.

I'm happy to implement the image.tag and keep Chart.appVersion when that's not available - would that be acceptable?