Add examples of the necessary, read-only IAM roles

Hi folks!

In the README, we say:

```
The script needs read-only access to the AWS organization where collection will be performed.

For database collection, the user running the script should have read-only permissions to connect to the database and there should be network connectivity configured between the databases and the ec2 instance running the script.
```

I think it can be useful to present an example (maybe a role?) that grants the necessary permissions.

Also, it appears that the README has formatting issues because of a misplaced code block.

Thanks!