Add eslint rule to avoid updating a ref in the render method

[michenly]

Motivation

The pattern come from these two issues:
Shopify/quilt#1813
facebook/react#18545

TL;DR
React core team is in discussion on adding warming for this and we can stop the bleeding earlier by adding this as a lint rule.

🚫 fail lint:
mutate refs in render method.

✅ pass lint:
mutate ref in a useEffect