There are no samples for Data Catalog clients in the repository

[mesmacosta]

Data Catalog is a new product in GCP's Big Data family. There is a version for its cloud client library publicly available (@google-cloud/datacatalog), but no samples for it in this repository.

As an early adopter of this product, I would like to contribute by creating the datacatalog/cloud-client folder in repo's root and add the lookup_entry.js sample there.