anchor.diff:  * allow theme to control font size of dot leader in TOC
   * allow section to override outlinelevels for self and children using outlinelevels attribute on section
   * use value of author attribute for PDF info and pdfmark if locked by the API (#1778)
  -* allow path of ghostscript command to be controlled using `GS` env var (#1791)
   * only extend theme in extends hierarchy once unless modified with !important (#1800)
   * add print-optimized themes (default-for-print and default-for-print-with-fallback-font) (#1699)
   * add support for power operator in theme (with same precedence as multiply and divide) (#1813)
  
positive.code: 
  Compliance::
  
  * drop support for versions of Asciidoctor < 2 (#1552)
  * drop support for Ruby < 2.5 (which includes JRuby 9.1) (#1681)
  * release lock on ttfunk version (1.6 produces slightly different output from 1.5 for certain missing glyphs)
  * upgrade to Prawn 2.3.0 (which adds OTF font support), then to Prawn 2.4.0
  * upgrade to prawn-svg 0.32 (adds support for Ruby 3 without a patch and for loading embedded images from a data URI)
  * upgrade to prawn-icon 3.0.x
  * use YAML.safe_load from Ruby stdlib instead of safe_yaml gem
  * drop deprecated Pdf module alias in API (leaving only PDF)
  * remove deprecated "ascii" fonts; only bundle the more complete "subset" fonts
  
negative.code: * add Ruby 3.1 to CI matrix; use as primary Ruby
  * test against Asciidoctor upstream (#1821)
  * skip tests for unreadable files when euid is 0
  
  == 1.6.1 (2021-09-04) - @mojavelinux
  
  Enhancements::
  
  * align footnotes block to the bottom of the page it is placed on (#1833)
  
  Bug Fixes::
  
  * patch Prawn to preserve leading null character when running on Ruby 3; preserves inline anchors when text is split by page (#1963)
  
  == 1.6.0 (2021-05-10) - @mojavelinux
  
  Enhancements::
  
  * allow path of ghostscript command to be controlled using `GS` env var (#1791)
  
  Bug Fixes::
  
  * do not hyphenate a hyphen when hyphenation is enabled (#1562)
  
  Compliance::
  
  * add support for Ruby 3 and drop support for Ruby < 2.5 and JRuby < 9.2 (#1681)
  * upgrade to Prawn 2.4.0 (adds support for Ruby 3 and OTF font support)
  * upgrade to prawn-svg 0.32 (adds support for Ruby 3 without a patch and for loading embedded images from a data URI)
  * upgrade to prawn-icon 3.0.x
  * release lock on ttfunk version (1.6 produces slightly different output from 1.5 for certain missing glyphs)
  * drop support for Asciidoctor < 2 (#1552)
  
  Build / Infrastructure::
  
  * run tests against pygments.rb 2.x in addition to pygments.rb 1.2.0
  
  == 1.5.3 (2020-02-28) - @mojavelinux
  
  