Add Readme file to each component

[michael-hawker]

Seems like NuGet expects to have actual readme files in the package now:

So, would be good for us to just have this in the root of each component folder to be used for NuGet and a good intro anyway of the component (from a public facing view vs. an internal repository/folder configuration view).

We should come up with a template for this we can re-use easily:

• Probably good to start with some general info about the Toolkit and a pointer to this repo.
• Provide an overview of what the component contains/does
• Show a short copy/pastable example of code to use the component (namespace included)

https://devblogs.microsoft.com/nuget/add-a-readme-to-your-nuget-package/#add-a-readme-to-your-package