bundle size
Hi, I've been using phosphor-react in some projects and I identified some bundle size problems.. Analysing the bundle I could realize that phosport-react is using almost 60% of the space used.

I don't know it's the expected behavior so I opened this issue to report this situation!

![bundle-size-phosport](https://user-images.githubusercontent.com/13206713/119356660-1093fd00-bc7d-11eb-9515-ba29e51a8bf0.png)






