* Edit and review package docs.
* Filter out testa and internal namespaces.
* remove offsetStep field that was accidentally revivified
* Resolving review comments
* Update com.unity.ml-agents/Runtime/Agent.cs
* fix trailing whitespace
* Revised Agent class intro and step description
* Fixed a few missed comments.
* removed prerelease warning
Co-authored-by: Chris Elion <chris.elion@unity3d.com>