React list virtualisation in 46 lines using IntersectionObserver

I've been using this technique in production on my app NightCafe Creator[1] for 9+ months with great success, so I decided to turn it into a package.

It's far easier to integrate than the current go-to virtualization options, which often require you to re-architect a lot of how your list works.

1. https://creator.nightcafe.studio