AWS Slack notifications for Amplify deployments

[pcaversaccio]

Setup of Slack notifications for the new channel #dev-aws-notifications for the Amplify deployments. Reference: https://dev.to/aws-builders/enable-slack-notifications-for-aws-amplify-deployments-5a0l.

[pcaversaccio]

Should be implemented for develop as well as for main.

[ttattl]

Can do without Backend @locpnh1995

[locpnh0409]

Note Todo.