Create docker images for Helm 2.16 and Helm 3.2

[mmingorance-dh]

We are using your available docker image to validate our Helm charts and find some API deprecations, however your current only available image was build using alpine/helm running Helm 2.14.

I'm using .Capabilities.KubeVersion.GitVersion to give some more flexibility to my chart, however since your image is running helm 2.14, I can't template a correct version of my chart for Kubernetes API versions higher than 1.14.

I would like to ask you to build some 2 new docker images, one with Helm 2.16 (for people still running Helm 2) and Helm 3.2

Thanks!

[mmingorance-dh]

@garethr could you please support?

[mmingorance-dh]

Maybe this PR (https://github.com/instrumenta/helm-conftest/pull/7) + a Release could work?

If this works, we could merge this other PR (https://github.com/instrumenta/helm-conftest/pull/8) as well, after (https://github.com/instrumenta/helm-conftest/pull/7) is merged.

[max-rocket-internet]

Or maybe we can have both versions 2 and 3 in the same docker image and the user can choose somehow?