Adding Verify:Pipeline Authoring alerts to Slack

Using as reference the instructions noted here, I want to add alerting to our #g_pipeline-authoring_alerts channel so that the team can have insight into when our components are violating their SLOs. This will help with being as proactive as possible to ensure error budgets are staying healthy.

@reprazent - if you can please review, update anything additional I may have missed, approve and merge, that would be greatly appreciated! Thanks again for your continued support. 🙇