message: use URLSearchParams ponyfill
diff: import React from 'react'
  import classnames from 'classnames'
  +import URLSearchParams from 'url-search-params'
  const IMAGE_BASE_URL = 'https://avatars.githubusercontent.com/'
  function getImageURL(username, params) {
  - const query = params ? `?${new URLSearchParams(params)}` : ''
  + const query = params ? '?' + new URLSearchParams(params) : ''
  return `${IMAGE_BASE_URL}${username}${query}`
  }
  