Docs feedback: Suggest using official AWS Images

Hey there,

i would suggest to add information about the offical amazon images also on the page about Serverless / AWS deployment.

With those the building would take place in an environment that is the same like where it will be deployed, no installing of AWS/SAM CLI is needed.

For example:

• https://hub.docker.com/r/amazon/aws-sam-cli-build-image-nodejs12.x
• https://hub.docker.com/r/amazon/aws-sam-cli-build-image-python3.8

If okay I would add another section to the AWS SAM part.

Cheers, michael