Adding an example of ReAct using Llama 2

Short explanation of ReAct
Setup and configuration to use Amazon Bedrock
Example of using the Bedrock api via langchain
Setup for use of DuckDuckGoSearchRun, WikipediaAPIWrapper, and PythonREPL.
Created a pattern for the model to follow in order to use the tools and do reasoning similar to CoT.
Cleaned up and formatted the generated text before giving it to the corresponding tool.