Run e2e tests in CI

[tstirrat15]

There are e2e tests for this repo, but we aren't running them.

[tstirrat15]

We should be able to do this using the vercel preview deploy - get vercel stood up and then point the e2e tests at them. We may have CORS issues with the save/load feature though.

[miparnisari]

I started working on this a while ago; the e2e tests pass locally but fail in Github 🤦‍♀️ #74