documentation request: Add more links to services

[EmilHvitfeldt]

This is a more general request around the whole package documentation. I think it would be helpful for the functions that use services outside of the package, to link to those services.

So the Posit Connect functions vetiver_deploy_rsconnect() and vetiver_create_rsconnect_bundle() should link to Posit Connect.

Likewise for the Amazon SageMaker functions.