+ sign in the filename - won't work with Windows

[consideRatio]

In #52 I added a + sign to the helm chart version, but the Helm chart version is used to construct a filename when we use --publish-chart. If this would be done on a windows computer, we would crash I think.

We should probably when working with the filename instead build to a filename where we replace + with _. What's important though, is that everything still works when updating and adding the files to index.yaml, so that the chart version we get from there still relies on +.

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Wait, it may work... I don't know.

[consideRatio]

We no longer use + signs, but it wouldn't been an issue anyhow I think.