Modal breaks popovers, dropdowns

It appears that react-modal2 breaks dialogues (components that also use react-gateway) that require focus (e.g., inputs). This seems to be an effect of [Modal.js#L10](https://github.com/cloudflare/react-modal2/blob/1eba22319878259daa20af32445bc15909567b54/src/Modal.js#L10).

I'm not sure if I've seen this from other libraries, but it seems unnecessary. I also didn't find any tests for this 🤔 .

Anybody else having issues with this? 😓