refs https://github.com/TryGhost/Team/issues/3504
This migrates comments-ui to TypeScript. Only `App.js` is left to
migrate, but since this isn't using hooks yet, it will need a bigger
rewrite so this will need to happen in a separate PR.
refs https://github.com/TryGhost/Team/issues/1780
This commit adds some Cypress tests as a POC to the project. If we decide to go with Cypress, we can add more tests to cover the rest of the codebase. The main reason to have a E2E framework is that some editor related UI is hard to test with the React tests because it uses JSDOM.