spanFn = (value) => {
  if (Array.isArray(value)) {
    return value.map(v =>
      v === 'auto' ? 'auto' : `span ${v}/span ${v}`
    )
  } else {
    return value === 'auto' ? 'auto' : `span ${value}/span ${value}`
  }
}
@description Map "span" values to accommodate breakpoint values
@param {Array} value
@returns {(String|Array)} String or Array of breakpoint values