Add Prout to know when PRs are deployed or overdue

[rtyley]

Adds Prout, to let us know when our changes don't ship as expected, or when they are ready to check in Production!

Some other recents PRs enabling Prout on repos:

• https://github.com/guardian/permissions/pull/174
• https://github.com/guardian/dotcom-rendering/pull/9692

[prout-bot]

Seen on Rule Manager (merged by @rtyley 28 minutes and 9 seconds ago) Please check your changes!

[prout-bot]

Overdue on Checker (merged by @rtyley 28 minutes and 9 seconds ago) What's gone wrong?