Clarify classic vs new-Studio and add Docker install example

[athewsey]

Issue #, if available: N/A

Description of changes:

• Add new install-docker-local-mode example showing how to install Docker CLI tools to enable SageMaker Local Mode (available as of December/re:Invent)
• Initial draft re-structure of the root README to clarify that existing samples mainly only support Studio Classic to date and haven't been ported (yet?). Add a bit of guidance on how to get started with LCCs in general since that still seems to be a learning curve for customers with the current SageMaker DevGuide

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[durgasury]

Updated the Readme and linked to the new Studio LCC repository for JupyterLab applications. Please submit the Docker PR to the new repository. Thanks for your contribution!