Investigate options for creating a banner for outages/slowness

[lbeaufort]

@LindsayYoung suggested we might want to create a banner for when we're experiencing production issues. Here's an article I found with examples: https://www.smashingmagazine.com/2009/06/effective-maintenance-pages-examples-and-best-practices/
cloud.gov uses statuspage.io: https://cloudgov.statuspage.io/

This is a research issue to determine the best way to inform the public of site outages or periods of slowness. We would want to handle an API outage and a whole-site outage (see this cloud.gov outage)

One option is to create a "status page" in Wagtail where we can update the site status. However, this wouldn't work in case of a cloud.gov outage.

@ccostino had the idea of putting a page in s3 in case of a cloud.gov outage.