add schedule job that posts into slack about any software not updated

[leighmcculloch]

From time to time folks on other teams forget to update the quickstart image with their latest stable release for latest, or their latest rc or stable release for testing. Would be helpful if the devx team could catch this with an automated check, since checking for new versions is something that can be done via the github api.

One way to do this would be a scheduled job in this repo running in github actions that has a slack webhook to post into a channel.

Ideally if the alert would be posted directly into the slack channel of the team responsible for keeping the version updated.