Update AWS SAM - VS Code configuration

[MarcelStranak]

Add a point about the needed configuration for AWS SAM in VS Code, launch.json.

It is important to mention the dockerNetwork property, which initiates the LocalStack container to execute the SAM local invoke command in the same network as the LocalStack container. See https://docs.aws.amazon.com/cloud9/latest/user-guide/sam-debug-config-ref.html.

Example:

{
            "type": "aws-sam",
            "request": "direct-invoke",
            "name": "Job dispatcher lambda",
            "invokeTarget": {
                "target": "code",
                "projectRoot": "${workspaceFolder}",
                "lambdaHandler": "lambda/lambda.handler"
            },
            "lambda": {
                "runtime": "python3.8",
                "payload": {},
                "environmentVariables": {
                    "ENDPOINT_URL": "http://localstack:4566/",
                    "S3_ENDPOINT_URL": "http://s3.localhost.localstack.cloud:4566/",
                    "AWS_ACCESS_KEY_ID": "test",
                    "AWS_SECRET_ACCESS_KEY": "test",
                    "AWS_SESSION_TOKEN": "test",
                    "AWS_REGION": "us-east-1",
                    "MAIN_DOCKER_NETWORK": "localstack-network"
                }
            },
            "sam": {
                "dockerNetwork": "localstack-network"
            }
        }