Add e2e browser tests

[asfaltboy]

It only took a couple of years, but I came back and completed this 2-day task of setting up some end-to-end tests

The next step is to reap value from it by adding a test case for the annoying "missing first form" bug I just noticed

[asfaltboy]

Consider switching to Playwright:

• https://github.com/microsoft/playwright-python
• https://devblogs.microsoft.com/python/announcing-playwright-for-python-reliable-end-to-end-testing-for-the-web/
• https://playwright.dev/python/docs/ci#ci-configurations