Add Apache v5 Client Sample documentation

[acm19]

Adds missing Apache v5 documentation to the README, last missing bit of the new supported client.

Pull Request Checklist:

• [ ] I have added a contribution line at the top of CHANGELOG.md.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[acm19]

@dblock release coming after this one.