Add support for adding task roles to the task

[djt5019]

Hi, I've tried using your module and it's pretty solid. The one
thing I noticed is that the module did not allow for setting a
task role. Without this the container is not able to interact with
the various AWS APIs, so some code was kicking back errors.

This addition will allow your task to interact with the metadata api
as well as other AWS services. This role is what the container will
assume when it is running.

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-iam-roles.html

[acepace]

@djt5019 it doesn't seem like anyone is supporting this. Do you mind forking this module?