Possible improvement to the guide

[Charlie Bowman]

While doing some preliminary work on a future project, and attempting to strictly and carefully follow the guide, I reached a friction point at "Step 12" (Add a list of illustrations).

I had marked up my body file with <img> and <figure> tags, and attempted to use the the "se build-loi" tool, which created the file, but had no illustrations in the list. After looking through the code of the tool, I figured out the reason was that the tool uses the spine to decide which files to look at, and since I wasn't yet at "Step 19. Build the manifest and spine," the spine didn't include the file I had marked up with the illustration tags.

Maybe a note should be included that if the producer needs to make a List of Illustrations, the build-loi tool isn't going to work at that point.