Helm Chart Repository API version format incorrect

The API version that is used in the Helm Chart Repository index.yaml is in the incorrect format. It is set as "1.0" when it should be "v1".

This breaks Octopus Deploy's Helm support, specifically the Helm Feed.

It is set in the API_VERSION class constant of CreateIndexServiceImpl in this line: https://github.com/sonatype-nexus-community/nexus-repository-helm/blob/b7afdc5117c63a6ac35a295c4f844bed6bac3e83/nexus-repository-helm/src/main/java/org/sonatype/repository/helm/internal/createindex/CreateIndexServiceImpl.java#L65

Inspecting the sources of the helm command-line utility, under the repo sub-command, specifically the repo index command, we see that that command gets the version string from the APIVersionV1 constant, which is "v1" in this line: https://github.com/helm/helm/blob/59447f850c88251afcca9a67b8ce44131a73c46a/pkg/repo/index.go#L41