Add getting started guide for SageMaker Hyperpod

[EmilyWebber]

Should include instructions for

1. How to create and manage a cluster for people who are completely new to Hyperpod
2. How to execute, monitor, and troubleshoot jobs with trn1 and NxD
3. A small test suite so we know the default instructions are working

[flamingofugang]

PR created: #29