Use liquid-lua to generate acknowledgements_epub.md, which is used by
pandoc to build the EPUB book. Also stop using the '{%-' / '-%}'
syntax, which liquid-lua does not support, in templates.
Also add a vertical space between the first bullet in each bulleted
list so pandoc recognizes bulleted lists as such. This has no effect on
the the website.
The EPUB is created with `pandoc` in combination with Lua filters, which
rewrite the abstract syntax tree to be more suitable for EPUB creation.
In particular all headings in the markdown files `part[123]/*.lagda.md`
are shifted up by 1 (e.g., level 1 heading -> level 2 heading), so that
we can make a level 1 heading for Appendix, Frontmatter, and different
parts of the book. This is done to match the structure on the website [1].
Syntax highlighting is done using pandoc's builtin syntax highlighter
(which uses the Haskell library `skylighting`). In other words, we do
not use `highlight.sh`, so the syntax highlighting is slightly different
than the website version of the book. This could certainly be dealt with
later.
What follows is a list of things that are currently broken, which is
probably not exhaustive:
- The `Acknowledgements` section is broken.
- Embedded fonts don't work. They're necessary for some ereaders, like my old Sony PRS-300.
- All inline links are broken. I could rewrite them with a Lua filter
and some regex, although that's not very nice :)
- `epubcheck` validation fails for a variety of reasons.
Closes#112.
[1]: https://plfa.github.io/
[2]: https://github.com/w3c/epubcheck
