add support for replicated repos

[bashims]

The current implementation of helms3 does not support S3 bucket replicated content. Ideally we would be able to leverage helm's ability to fetch charts using relative URLs (helm/helm#3057)

It may in fact make sense to make all URLs relative, but for now my proposal is to make toggling this feature using a flag.

[bashims]

Here is the current help output from my proposed change:

 ./bin/helms3 reindex --help
usage: helm s3 reindex [<flags>] <repo>

Reindex the repository.

Flags:
  --help        Show context-sensitive help (also try --help-long and --help-man).
  --timeout=5m  Timeout for the whole operation to complete. Defaults to 5 minutes.

                If you don't use MFA, it may be reasonable to lower the timeout for the most commands, for example to 10 seconds.

                In opposite, in cases where you want to reindex big repository (e.g. 10 000 charts), you definitely want to increase the timeout.
  --acl=""      S3 Object ACL to set on the Chart and Index object.

                For more information on S3 ACLs please see https://docs.aws.amazon.com/AmazonS3/latest/dev/acl-overview.html#canned-acl
  --relative    Reindex with relative URL (useful when S3 buckets are replicated)

Args:
  <repo>  Target repository to reindex

[bashims]

Link to the PR: #122

[hypnoglow]

The plugin version 0.10.0 is released.