Processing:
  * Add dash filter to handle en-dash.
  * Optionally cap over-long titles in headers.
  * Mark bad links (not only warn at build) in flightcheck+draft mode.
  * Warn about possible HTML escapes in content (e.g. &#\d+; or %{HEX}).
  * Maybe comply with PDF/A-1b (or newer).
    + Include to preflight online test against e.g.
      <https://www.pdf-tools.com/pdf/validate-pdfa-online.aspx>
  * Generalize pandoc-memoir filter.
    + Enable matter injection conditional to environment variable.
    + Define Headline regexes via environment variable.
  * Verify that pandoc-citeproc is applied only once.

Content modelling:
  * Consider use typographic enhancement tunings:
    + icomma - avoid automagic space after comma (e.g. money amount).
    + ellipsis - ensure balanced space around ellipsis.
    + csquote (with explicit british: class ignored with polyglossia).
    + xspace - ensure space after superscript/subscript characters.
    + numprint - space/comma separated enumeration.
    + cite - enhanced citation handling.
  * Support numbered lists with complex starting point.
    + "Mandatory Characteristics" list ideally should be 4.1.1-4.1.6.
  * Redirect bibtex parsing warnings/errors to STDERR.
    + Example: Title section containing doublequote.

Styling:
  * Curly quotes.
    + Hack curl singlequote-begin in "‘Towards Interoperability…".
    + Hack re-flatten singlequote in "Citizens' Rights" and "O'Reilly".
    + Ensure "Sophie in 't Veld" uses apostrophe.
  * Use standardized layout for bibliography.
  * no quoting around origin link string.
  * Use A or B form factor (not Letter) for ebook page size.
  * Conditionally set narrow margins for mainmatter of ebook target.
    + \setlrmarginsandblock{1cm}{*}{*}
  * Maybe visually wrap URLs in <> to distinguish trailing punctuation.
  * Adapt colophon for each target (type measure vary).
  * Penalize pagebreak between single line and list.

Repository:
  * Add README
  * Add proper copyright and licensing
    + Code: AGPL-3+.
    + Design: CC-by-sa-4.0.
  * Move to source.jones.dk.

Release:
  * Repository stuff.
  * colophon facts.
  * No orange or yellow markup!