[FEATURE] Notifications for updated packages

[mwarkentin]

Is your feature request related to a problem? Please describe.
It would be nice if there was an event published somewhere when a package is updated.

Describe the solution you'd like
Ideally there would be an SNS topic (or one per package) which we could subscribe to in order to add some automation (lambda) or notifications (email, slack) when new versions of packages are published.

Additional context
There may be some additional costs (maybe AWS could provide credits): https://aws.amazon.com/sns/pricing/