added 4 more commands

/itemedit skullowner [owner]
sets owner's texture skull in your hand (must be a Player skull), texture might glich if that happens just place the head and break it to update the skin

/itemedit bookauthor [author]
sets the author of the book in your hand

/itemedit booktitle [title]
sets the title of the book (max 16 characters) in your hand

/itemedit booktype <type>
set the type of a book in your hand, types are:
COPY_OF_COPY, COPY_OF_ORIGINAL, ORIGINAL, TATTERED
and can be found here:
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/inventory/meta/BookMeta.Generation.html