message: Makes this a proper mixin
diff: +import { css } from 'styled-components';
  +
  export default {
  size: {
  root: {
  @@ -30,7 +32,7 @@ export default {
  },
  mixins: {
  - antialiased: `
  + antialiased: css`
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  `,
  