AWS Slack notifications for cost anomaly detection

[pcaversaccio]

Setup of Slack notifications for the new channel #dev-aws-notifications for cost anomaly detection. Reference: https://aws.amazon.com/aws-cost-management/resources/slack-integrations-for-aws-cost-anomaly-detection-using-aws-chatbot/

[pcaversaccio]

I think this is getting more and more important right now. Should be done for dev and prod AWS account.

[ttattl]

Noted.