* Move mix-ins to its own chapter
I don't think it belongs to wheat one which is already packed,
Schwarzbort for once is usually with seeds added.
Once we have more pics it will be even more cramped in the wheat
chapter.
* Fix TeXnicalilities in mix-ins chapter
looooong lines, no use of sinunitx, abbreviations, etc..
* Fix typo
* Update book/book.tex
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Co-authored-by: Hendrik Kleinwaechter <hendrik.kleinwaechter@gmail.com>
