Update install docs to mention samples and link to the forum for feedback (#5091)

Co-authored-by: Chris Elion <chris.elion@unity3d.com>

README.md

 using the ML-Agents Toolkit or have a specific feature request, please
 [submit a GitHub issue](https://github.com/Unity-Technologies/ml-agents/issues).
 
+Please tell us which samples you would like to see shipped with the ML-Agents Unity
+package by replying to
+[this forum thread](https://forum.unity.com/threads/feedback-wanted-shipping-sample-s-with-the-ml-agents-package.1073468/).
+
+
 Your opinion matters a great deal to us. Only by hearing your thoughts on the
 Unity ML-Agents Toolkit can we continue to improve and grow. Please take a few
 minutes to

docs/Getting-Started.md

 If you haven't already, follow the [installation instructions](Installation.md).
 Afterwards, open the Unity Project that contains all the example environments:
 
-1. Launch Unity Hub
-1. On the Projects dialog, choose the **Add** option at the top of the window.
-1. Using the file dialog that opens, locate the `Project` folder within the
-   ML-Agents Toolkit and click **Open**.
+1. Open the Package Manager Window by navigating to `Window -> Package Manager`
+   in the menu.
+1. Navigate to the ML-Agents Package and click on it.
+1. Find the `3D Ball` sample and click `Import`.
 1. In the **Project** window, go to the
    `Assets/ML-Agents/Examples/3DBall/Scenes` folder and open the `3DBall` scene
    file.

docs/Installation.md

 The ML-Agents Toolkit contains several components:
 
 - Unity package ([`com.unity.ml-agents`](../com.unity.ml-agents/)) contains the
-  Unity C# SDK that will be integrated into your Unity scene.
+  Unity C# SDK that will be integrated into your Unity project.  This package contains
+  a sample to help you get started with ML-Agents.
 - Unity package
   ([`com.unity.ml-agents.extensions`](../com.unity.ml-agents.extensions/))
   contains experimental C#/Unity components that are not yet ready to be part
 packages, but you may choose to clone the repository if you'd like download our
 example environments and training configurations to experiment with them (some
 of our tutorials / guides assume you have access to our example environments).
+
+**NOTE:** There are samples shipped with the Unity Package.  You only need to clone
+the repository if you would like to explore more examples.
 
 ```sh
 git clone --branch release_14 https://github.com/Unity-Technologies/ml-agents.git