title: Wordpress add responsive srcset header image to theme
body: <p>WP introduced support for srcset in version 4.4 for Thumbnails and Post images. But I can't find a way to make the page header responsive. Here is how I embed the Page header:</p>
  
  <pre><code>&lt;img src="&lt;?php header_image() ?&gt;" alt=""&gt;  
  </code></pre>
  
  <p>This loads the header image (which can be uploaded in the backend > Design > Customise) in an <strong>src</strong>. But I'd rather include all custom image sizes (that I added in functions.php) of this image and put them in an <strong>srcset</strong> attribute. But there seems to be only one size for the header?</p>