RFC: E2E Testing

## 💥 Proposal

As the codebase grows, it would be beneficial to add more/different kinds of testing strategies. I think expanding E2E testing with an automation tool like Selenium could improve coverage.

[NextJS](https://github.com/vercel/next.js/blob/canary/contributing.md#to-run-tests) implemented this style of tesing on top of all of their other unit tests and it works very well.

I can start a draft if this gets approved because I have an idea on how it could be implemented.

### Have you read the [Contributing Guidelines on issues](https://github.com/facebook/docusaurus/blob/master/CONTRIBUTING.md#reporting-new-issues)?

Yes