message: add whitespace props to UnderlineNav; lint
diff: import React from 'react'
  import PropTypes from 'prop-types'
  import classnames from 'classnames'
  +import {mapWhitespaceProps} from './props'
  export const ITEM_CLASS = 'UnderlineNav-item no-underline'
  export const SELECTED_CLASS = 'selected'
  export default function UnderlineNav(props) {
  - const {actions, align, children, full, label} = props
  + const {actions, align, children, full, label, ...rest} = props
  + const {className} = mapWhitespaceProps(rest)
  + const classes = classnames(className, 'UnderlineNav', align && `UnderlineNav--${align}`, full && 'UnderlineNav--full')
  const mappedChildren = React.Children.map(children, child => {
  const {className} = child.props
  @@ -24,10 +27,7 @@ export default function UnderlineNav(props) {
  })
  return (
  - <nav
  - className={classnames('UnderlineNav', align && `UnderlineNav--${align}`, full && 'UnderlineNav--full')}
  - aria-label={label}
  - >
  + <nav className={classes} aria-label={label}>
  <div className="UnderlineNav-body">{mappedChildren}</div>
  {actions && <div className="UnderlineNav-actions">{actions}</div>}
  </nav>
  