Supporting several S3 buckets

[oripwk]

Hi,

Thanks for this awesome plugin.

We have a use-case where we need to upload the same set of files to two separate buckets.
Unfortunately the plugin doesn't support this.

Is it possible maybe to add another SettingKey s3AdditionalHosts to support such cases?

At the moment the only workaround is using sbt commands as described here which is quite painful.

Thanks