[doc] Updated deployment guidance for SAM

AWS SAM seems to have evolved since the documentation and examples have been written, and we could benefit from guidance in taking advantage of features like Makefile builds, 'sam sync' and 'sam local start-api'

I've created a Makefile build that works reasonably well, and takes advantage of incremental builds, but it doesn't work with the 'sam sync' command (it continuously builds and deploys).

Below is my template.yaml and Makefile - with this, I can use the following commands:
- sam build
- sam deploy
- sam local start-api

template.yaml:
```
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: SAM Template for APIGateway Lambda Example

Resources:
# Lambda function
# .build/plugins/AWSLambdaPackager/outputs/AWSLambdaPackager/LinksService/LinksService.zip
LinksService:
Type: AWS::Serverless::Function
Metadata:
BuildMethod: makefile
Properties:
CodeUri: .
Timeout: 60
Handler: swift.bootstrap # ignored by the Swift runtime
Runtime: provided.al2
MemorySize: 512
Architectures:
- arm64
Environment:
Variables:
# by default, AWS Lambda runtime produces no log
# use `LOG_LEVEL: debug` for for lifecycle and event handling information
# use `LOG_LEVEL: trace` for detailed input event information
LOG_LEVEL: debug
Events:
HttpApiEvent:
Type: HttpApi

Outputs:
# print API Gateway endpoint
APIGatewayEndpoint:
Description: API Gateway endpoint URL
Value: !Sub "https://${ServerlessHttpApi}.execute-api.${AWS::Region}.amazonaws.com"
```

Makefile (changing into the WORKING_DIR each time to use incremental builds - `sam build` creates a new temp directory with each build):
```
WORKING_DIR = $(PWD)

build-LinksService:
cd $(WORKING_DIR) && swift build
cd $(WORKING_DIR) && swift package archive --allow-network-connections docker
mv $(WORKING_DIR)/.build/plugins/AWSLambdaPackager/outputs/AWSLambdaPackager/LinksService/* $(ARTIFACTS_DIR)
```