Add Cloudonaut IAM reference (#447)

* Add Cloudonaut IAM reference

* Tweak language.

README.md

@@ -591,6 +591,7 @@ We cover security basics first, since configuring user accounts is something you
 -	🔹**Use IAM roles for EC2:** Rather than assign IAM users to applications like services and then sharing the sensitive credentials, [define and assign roles to EC2 instances](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html) and have applications retrieve credentials from the [instance metadata](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html).
 -	Assign IAM roles by realm — for example, to development, staging, and production. If you’re setting up a role, it should be tied to a specific realm so you have clean separation. This prevents, for example, a development instance from connecting to a production database.
 -	**Best practices:** AWS’ [list of best practices](https://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html) is worth reading in full up front.
+-	**IAM Reference:** [This interactive reference for all IAM actions, effects, and resources](https://iam.cloudonaut.io/) is great to have open while writing new or trying to understand existing IAM policies.
 -	**Multiple accounts:** Decide on whether you want to use multiple AWS accounts and [research](https://dab35129f0361dca3159-2fe04d8054667ffada6c4002813eccf0.ssl.cf1.rackcdn.com/downloads/pdfs/Rackspace%20Best%20Practices%20for%20AWS%20-%20Identity%20Managment%20-%20Billing%20-%20Auditing.pdf) how to organize access across them. Factors to consider:
 	-	Number of users
 	-	Importance of isolation