Add type aliases for cloud object store uris

Add a type alias for Cloud Object Store URIs, e.g., (s3://mybucket/myfile).

These URIs are commonly used as sources for files, packages, etc. in Puppet modules. Some organizations even keep all sources in a specific cloud object store like s3 in order to limit downloads from the internet when applying a Puppet catalogue across potentially thousands of nodes.

It would be useful to have a type alias for these URIs.