Update rollup

[emmatown]

What:

Update Rollup.

Why:

Previously, in the esm bundle, rollup generated an import for emotion like this.

import * as emotion from 'emotion'

This can't work with tree shaking since every export of emotion is used. (even though tree shaking won't do very much for the emotion package since most of the code is used by all the exports, this is mainly to make tree shaking work(hopefully) for #453 since tree-shaking will actually help that)
Now, rollup generates an import like this

import { css, getRegisteredStyles } from 'emotion'

so it should work better with tree shaking.

How:

yarn upgrade-interactive --latest

Checklist:

• Documentation N/A
• Tests N/A
• Code complete

There is a small size increase to the UMD build but it's to the way the UMD is defined and checking for a default import, so it won't affect the way the majority of consumers will use it, with ESM.

[tkh44]

LGTM