anchor.diff:  * reduce min font size in base theme
   * allow theme to configure the minimum height required after a section title for it to stay on same page (#1210)
   * convert hyphen to underscore in theme key for admonition icon type (#1217)
  -* always resolve images in running content relative to themesdir (instead of document) (#1183)
  +* always resolve images in running content relative to `themesdir` (instead of document) (#1183)
   * fix placement of toc in article when doctitle is not set (#1240)
   * honor text alignment role on abstract paragraph(s)
  -* don't insert blank page at start of document if media=prepress and document does not have a cover (#1181)
  -* insert blank page after cover if media=prepress (#1181)
  +* don't insert blank page at start of document if `media=prepress` and document does not have a cover (#1181)
  +* insert blank page after cover if `media=prepress` (#1181)
   * add support for stretch role on table (as preferred alias for spread) (#1225)
   * include revremark on title page if specified (#1198)
   * allow theme to configure border around block image (#767)
  
positive.code: * Resolve bare image-related attribute values relative to base_dir
  * Only allow Prawn SVG to fetch remote images if the allow-uri-read attribute is set (#548)
  * Introduce page_margin_inner and page_margin_outer keys to theme
  * Start title page, toc, main content, parts, and chapters on recto page when media=prepress and doctype=book
  * Allow default font style for table to be set via theme (table_font_style)
  * Use correct default bullet per nested unordered list level (#529)
  * Call start_new_part at start of each book part
  * Delegate to layout_part_title method to layout part title
  * Don't match a special section as a chapter unless the doctype is book
  * Fix list marker placement when list item touches bottom of page
  * Eliminate excessive spacing between list items that contain nested lists
  * Drop lines in running (header/footer) content with unresolved attributes (#522)
  * Ensure start_new_chapter is always executed at a chapter transition (#524)
  * Add support for root xref (e.g., &lt;&lt;included-doc#&gt;&gt;) (#521)
  * Prevent block from spilling to next page if there's no more content (#361)
  * Add support for px units to pdf-page-size attribute
  
negative.code: * scale SVG background image to fit page in the same way raster image is scaled (#765)
  * allow page background size to be controlled using image macro attributes (#1117)
  * allow page background image position to be controlled using position attribute on image macro (#1124)
  * add support for `fit=cover` for cover, page background, and running content images (#1136)
  * change default background image position to center (#1124)
  * allow cover image position to be controlled using position attribute on image macro (#1134)
  * change default cover image position to center (#1134)
  * allow cover image size to be controlled using fit, pdfwidth, and width attributes; don't scale image by default (#1134)
  * set `enable_file_requests_with_root` and `enable_web_requests` options for all SVGs (#683)
  * automatically set `pdf-stylesdir` if `pdf-style` ends with .yml and `pdf-stylesdir` is not specified (#1126)
  * replace hyphens with underscores in top-level theme keys
  * allow hyphens to be used in variable references in theme (#1122)
  * allow theme to control background and border of inline code (literal) (#306)
  