Document additional examples for multi repo structure

[interurban]

Great feedback from @dabcoder in Pulumi Discussions:

Discussed in pulumi/pulumi#17742

^{Originally posted by dabcoder November 12, 2024}
In this section of the public documentation, it is mentioned that some users prefer to manage a single Pulumi project using more than one repository.
Whilst there is an example further down below on the same page for mono repo environments, it would be good to add another example of a multi repo structure. Perhaps with a use case where a Pulumi package/component is authored in a specific repository and the configuration of the infrastructure component to create is set in another repo?