Add example to add iam policies to task role

[EvilPlankton]

Found a bug? Maybe our Slack Community can help.

Describe the Bug

When using secrets list in a container definition the container gets an permissions error trying to access SecretsManager when the task is instantiated

Expected Behavior

The container should be able to retrieve values from SecretsManager

Steps to Reproduce

Create a container definition with a valueFrom using an ARN in secretsmanager. When the task is run (in Fargate) by the service it will fail with a permissions error on the _exec role.

Screenshots

N/A

Environment (please complete the following information):

N/A

Additional Context

N/A