message: add listStyle system prop
diff: import React from 'react'
  +import {style} from 'styled-system'
  import system from 'system-components/emotion'
  import {default as defaultTheme} from './theme'
  @@ -139,6 +140,12 @@ export function withoutPropTypes(Component, props) {
  return Component
  }
  +export const listStyle = style({
  + prop: 'listStyle',
  + cssProperty: 'list-style',
  + key: 'listStyles'
  +})
  +
  function guardDoubleRender(Component) {
  function render(props) {
  const {is, ...rest} = props
  