Switching Styled Components to Emotion to improve support for Gatsby & React Native Environments

I wanted to see if there has been any discussion about moving the `styled` functionality to `emotion`, instead of `styled-components`?

I noticed rimble uses `styled-system` which is super awesome - love the work jxnblk does!

Recently he has made major improvements to his underlying design assumptions and brought everything into `theme-ui` which in his opinion, improves on his original `styled-system` assumptions.

https://theme-ui.com

The primary styling system is `emotion` however. Not `styled-components`.

However, the switch to `emotion` would bring a couple of benefits I think might be useful for Rimble.

First. jxnblk is full-time on Gatsby, from what I can tell spending all his efforts improving the `theme-ui` system and including interesting features with `mdx`. It would be great to add his improvements to the library pre the upcoming Gatsby announcements for their platform launch. Could be a lot of great improvements that could be picked up along the way.

Second, `emotion` provides better css primitives that can map to React Native components. It would be cool and to try and create React Native Web prototype using the Rimble Component System in application similar to https://github.com/brunolemos/react-native-web-monorepo

Thoughts?