text: import React from 'react'
  import { useColorMode } from 'theme-ui'
  
  export default function Header() {
    const [colorMode, setColorMode] = useColorMode()
    return (
      <header>
        <button
          onClick={() => setColorMode(colorMode === 'light' ? 'dark' : 'light')}>
          Toggle {colorMode === 'light' ? 'Dark' : 'Light'}
        </button>
      </header>
    )
  }
  