Run end-to-end tests in atomic-server CI

[joepio]

Although the e2e tests are run in the atomic-data-browser CI, they are not being run here. This has previously led to broken docker builds before - and that harms the developer experience.

I think it would be not that hard to run the e2e tests here.

Options:

Dockerize e2e tests, load docker image

• Requires publishing yet another docker image

Git pull e2e tests, run yarn

• Will probably be pretty slow

[joepio]

Now that I've got #185 pretty much done, I think this is more manageable.

Still not sure what the best way forward is.

This is how the e2e are executed in atomic-data-browser:

      - uses: actions/setup-node@v2
        with:
          node-version: "14"
      - uses: bahmutov/npm-install@v1
      - run: npx playwright install-deps
      - run: yarn test

This means we need to run yarn, which means a package.json, and the tests themselves of course.

Seems a bit much. Is there a simpler way, maybe?

yes! There is npx playwright test tests/todo-page.spec.ts, which for some reason seems to take ages to run on my laptop. Bu anyway, that would remove the need for a package.json.

Getting the test file itself is still a matter of copy/paste, which will