DRAFT: Feature/crkrenn/quit for now

[crkrenn]

This branch implements a "quit for now" button. This is one of the 36 "priority" cards: https://github.com/compdemocracy/polis/issues/242

And, it passes all of the same non third-party e2e tests as edge. (Both fail the "shows the visualization after 7 participants" test.)

Please let me know what you think. Thanks!

-Chris