Add "Confluentinc" repo and charts

[agolomoodysaada]

All the Conluent inc helm charts are missing from the hub. They can be found here: https://github.com/confluentinc/cp-helm-charts

[sudermanjr]

This will have to made into a helm repository and added using the instructions here - https://github.com/helm/hub/blob/master/Repositories.md

[mattfarina]

This can also be added to the Artifact Hub, as well.

I filed confluentinc/cp-helm-charts#455 to ask them to add it. With that in mind, I'm closing this issue.