cr updload should be able to use custom tags

I was trying to use tags as v<sem_ver> to create a release on github with the helm chart plus some other files and then rebuild the index correctly with cr index. I didn't want to use the cr upload command because it does not allow to upload other files easily and another process was already in place to create the release with a meaningful release note, etc.

But I hit the following issue:

Currently due to some assumptions on release tags made by the cr index command (the presence of a - in order to split package name and version), it is not possible to use such kind of "simple tags" because passing --release-name-template "{{ .Version }} returns an index error here.

Proposed solution:

I think a user should be able to pass explicitly the package name (maybe as a template) and the package version as a template separately and if not provided fallback to the current assumption.