anchor.diff:  Required keys are provided by the base theme.
   Therefore, you only have to assign values to keys you want to customize.
   
  +[#keys-page]
   === Page
   
   The keys in this category control the size, margins and background of each page (i.e., canvas).
  
positive.code: 
  . Controls the color of the bullet glyph that marks items in unordered lists and the number for items in ordered lists.
  
  === Table
  
  The keys in this category control the arrangement and style of tables and table cells.
  
negative.code: |===
  |Key |Value Type |Example
  
  3+|[#key-prefix-admonition]*Key Prefix:* <<key-prefix-admonition,admonition>>
  
  |column_rule_color
  |<<colors,Color>> +
  