Location of status messages

[VirginiaDooley]

Issue and Steps to Reproduce

The status message is currently placed below the nav and is truncated by the site width. This would look better at the very top of the page, but before implementing, this change needs to be tested in conjunction with sites that have similar bars for language options.

https://user-images.githubusercontent.com/20044500/204319775-597e8f10-1dc3-44b2-84ce-a3bdab29a161.png

Ref DemocracyClub/EveryElection#1637

[symroe]

I think there are two uses for this one component:

1. As is: there are loads of times when a "flash message" is useful, like when a form is submitted and we want to show the user a message about it. This is what the Django messages framework does, and the current implementation works well for it.
2. Site wide or persistent messages, like "this is a dev site"

Both are useful so I think we need to document the two cases. With one, we put the HTML in the main element, towards the top, on the other we add it above the header.