Document AMI release process (runbook/playbook)

[mattlebeau-galois]

AC:

• Docs exist that can be exercised to add a new AMI or modify an existing one.
• README.md in the repo would be helpful on this.

[mattlebeau-galois]

EX: updating AMI DB in portal

• jump from bastion to Aurora serverless cluster
• document manual update procedure rather than creating any UI for this. Merge to master ??? profit

[mattlebeau-galois]

Got a link to the canonical document here, @alex-fivetalent ? (would like to attach it to the ticket before closing.)