Add docs on how to use Configuration API

[msfussell]

Please add documentation that is consistent with the other Go SDK docs on how to use the Configuration API.
The doc / example should live here: https://docs.dapr.io/developing-applications/sdks/go/go-client.

Consider also adding the Go example to How-to for https://v1-6.docs.dapr.io/developing-applications/building-blocks/configuration/howto-manage-configuration/

[unnsteinngardars]

Would very much appreciate good documentation on this like the other building blocks have. Also it would be nice to have both Self Hosted(CLI) and Kubernetes instructions.

[mikeee]

Looks resolved as of #386