anchor.diff:  * HIGH: style example block
   * HIGH: allow theme to be customized using stylesheet attribute
   * MEDIUM: headshot has too much top margin when at top of page (not below section title)
  -* MEDIUM: add landmarks nav list to nav.xhtml
   * support both jpg and png avatars
   * add docinfo support
   * add navigation links in meta, e.g.,
  
positive.code: * HIGH: use more thorough image path resolution
  * HIGH: move navigation_document method to Packager
  * HIGH: put shy marks after dashes to allow wrapping to occur in text justification
  * HIGH: why can't id on chapter document be specified using +[#name]+ syntax? (it only seems to recognize +[[name]]+)
  * MEDIUM: auto-space button in btn macro, or add icon & icon placement as attributes on btn macro
  * MEDIUM: move client sniffer JavaScript to file
  * MEDIUM: use the dfn element for defining a definition of a term (not just term class); see https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dfn
  
negative.code: = WORKLOG
  
  == TODO
  
  * add empty front matter page in kf8 version if one is specified to allow navigation to first entry from TOC
  * remove text justification hack (#92)
  * why can't we navigate to first chapter on Kindle from TOC?
  * add nav entry for cover if format != :kf8 ?
  * cleanup this sanitize XML stuff; move to Asciidoctor::Helpers?
  * allow role to be applied to chapter (which means the role must be on the document)
  * make sure every doc is assigned an ID (perhaps it already is) so we don't need to rely on the docname attr as a fallback
  * switch to epubcheck-ruby
   ** epubcheck-ruby 4.0.2
   ** supports options such as -q
   ** add -w option by default (perhaps allow additional options to be passed via the ebook-validate attribute)
  * store spine as map in references?
  * part vs chapter? a difference?
  
  * create a video to demonstrate Google Play Books read aloud reading complete sentences in books generated with Asciidoctor EPUB3
  
  