Step Functions

**Is your feature request related to a problem? Please describe.**
Integrating Step Functions is not currently supported, but is something I find myself using

**Describe the solution you'd like**
I would love it if Step Functions were to become officially supported to be provisioned and given access in the Amplify CLI.

**Describe alternatives you've considered**
I'm currently manually integrating the CloudFormation behind the scenes, or alternately using Terraform as a completely separate side application which then gets called from Amplify Apps.

**Additional context**
AWS Step Functions is a very powerful solution for a lot of backend processes that I have behind the apps I write. To be able to natively use it in Amplify would be such a big time saver. Looks like the CloudFormation itself for it is pretty easy, but using Lambdas in the state machine is something I'm still figuring out and I'm guessing is the more difficult implementation blocker to overcome.