anchor.diff:  * section-title
   * section-or-chapter-title
   
  -For example:
  +Here's an example that shows how these attributes can be used in the running footer:
   
   [source,yaml]
   ----
  
positive.code: NOTE: The background color spans the width of the page.
  When a background color is specified, the border also spans the width of the page.
  
  In addition to the document-level attributes defined in the AsciiDoc document, the following attributes are available when defining the content keys in the footer:
  
  * page-count
  
negative.code:   verso_content:
      left: '{page-number} | {chapter-title}'
  ----
  
  ==== Images
  
  You can add an image to the running header or footer using the AsciiDoc inline image syntax.
  Note that the image must be the whole value for a given position (left, center or right).
  It cannot be combined with text.
  
  Here's an example of how to use an image in the running footer.
  
  [source,yaml]
  ----
  footer:
    height: 0.75in
    image_valign: 2 # <1>
    recto_content:
      left: image:footer-logo.png[width=80]
      right: '{page-number}'
    verso_content:
      left: $footer_recto_content_right
      right: $footer_recto_content_left
  ----
  <1> You can use the `footer_valign` attribute to slighly nudge the image up or down.
  
  CAUTION: The image must fit in the allotted space for the running header or footer.
  Otherwise, you will run into layout issues.
  Adjust the width attribute accordingly.
  
  == Applying your theme
  
  