Create a proposal for WCs in React

[lastmjs]

React will consider a proposal to incorporate WCs: https://twitter.com/dan_abramov/status/959174566642966534

• [ ] Look at other RFCs to see how they are structured
• [ ] Review Rob Dodson's proposal for how React should handle attributes for inpsiration
• [ ] Start with the benefits WCs will provide
• [ ] Discuss the tradeoffs, and why the benefits still outweigh the tradeoffs
• [ ] Discuss how the implementation could work