Documentation - Explore Lambda Runtime Interface Emulator for local testing

[huntharo]

Motivations

• Developing locally is not easily possible for others due to the custom patch for the AWS LambdaTestTool for DotNet
• There may be a way to make this easier for others

Acceptance Criteria

• Check if the Lambda Runtime Interface Emulator supports Runtime, Extension, and Client APIs
• If so, add documentation on how to set this up and develop locally using it

Docs

• https://github.com/aws/aws-lambda-runtime-interface-emulator