Add a bunch of tests

[franknoirot]

We've gotten away with not having good, CI-blocking tests for this little site because we haven't changed much since we launched it. But we don't want it to break, so let's actually get some solid tests in. Cc @jacebrowning for guidance on setting up test monitoring and the proposed test suite, I can take a swing at proposing and writing some tests.

Try to make the test 🔺- or 🏆-shaped please.

[franknoirot]

First one we need is just an E2E recommended by @jacebrowning:

I think a single e2e test to auth, then basic prompt, then open in ZDS web would go a long way

[jessfraz]

another thing to ensure, that plausible and any other scripts are off in dev