message: add m + p utils to Label
diff: import React from 'react'
  import PropTypes from 'prop-types'
  import classnames from 'classnames'
  +import {mapWhitespaceProps} from './props'
  const colorScheme = (scheme, outline) => {
  if (outline) {
  @@ -18,9 +19,9 @@ const colorScheme = (scheme, outline) => {
  }
  export default function Label(props) {
  - const {outline, scheme, children} = props
  + const {outline, scheme, children, className} = mapWhitespaceProps(props)
  return (
  - <span className={classnames('Label', outline && 'Label--outline', colorScheme(scheme, outline))}>{children}</span>
  + <span className={classnames(className, 'Label', outline && 'Label--outline', colorScheme(scheme, outline))}>{children}</span>
  )
  }
  