Update Readme with example passing local AWS_PROFILE env var

Just started using this today. Dig the idea, and using a bash (or zsh in my case) alias doesn't require a change to workflow. Except for using multiple profiles.

Is your feature request related to a problem? Please describe. When working with multiple accounts, you need to pass the --profile flag with each command.

Describe the solution you'd like With docker you can add -e AWS_PROFILE to set the AWS_PROFILE env var to the value of your local terminal session.

Describe alternatives you've considered n/a

Additional context This works as is, this is just a suggestions to add to the readme.

Happy to submit a PR for this if you think it's worth adding.

Thanks.

Please push a PR for this and I'll get it merged.