title: How to use global css styles in shadow dom
body: <p>Shadow <code>dom</code> encapsulate css styles, selectors don't cross the shadow boundary. </p>
  
  <p><strong>Question:</strong> How to use global common css styles in shadow dom?<br>
  (suppose there are some common css styles which will be used across all pages (e.g.: font-family, h1, h2, clear, reset ...), how to make it works in shadow dom?)</p>