version of the notebooks using amazon bedrock

Added a version of the Prompt Engineering with Llama 2 that utilizes Amazon Bedrock
Added a getting started with Llama 2 on Amazon Bedrock which should help developers quickly get started with some reference documentation, setting up credentials, and ultimately using the bedrock client and client_runtime to perform a couple examples and show the diff between prompts run against Llama 2 13b chat vs Llama 2 70b chat