(Consider) Persist region in a cookie

[awwaiid]

We were saving ALL state into localStorage which was confusing. But now we don't save ANY state, and if you navigate to the site it doesn't remember what region you most recently selected. See if we can save the region in a cookie!

Note:

• Test out the /embed-demo.html path to make sure we don't break embedding
• If the embedded demo locks you to a region that's fine for it to be come your new default region, but you should be able to change regions on the full site

┆Issue is synchronized with this Trello card by Unito