Sign in: Preview that sign-in page will change soon #2403
Who is this PR for?
What problem does this PR fix?
There are awesome new designs for the sign-in page, but there's no notice to folks that this will be changing.
What does this PR do?
Adds a notice, with links to previews.
Screenshot (if adding a client-side feature)
Which features or pages does this PR touch?
Does this PR use tests to help verify we can deploy these changes quickly and confidently?