message: Mixes in flex-grow/shrink
diff: @@ -17,10 +17,14 @@ import {
  bgColor,
  textAlign,
  flex,
  + style,
  } from 'styled-system';
  import { neutralMargins } from 'react/styles/mixins';
  +const flexGrow = style({ prop: 'flexGrow' });
  +const flexShrink = style({ prop: 'flexShrink' });
  +
  export const mixin = css`
  box-sizing: border-box;
  ${display}
  @@ -31,6 +35,8 @@ export const mixin = css`
  ${maxHeight}
  ${space}
  ${flex}
  + ${flexGrow}
  + ${flexShrink}
  ${alignItems}
  ${alignSelf}
  ${justifyContent}
  