1.6

Added 1.18 compatibility and minimized NMS surface

It might still crash on newer versions if you try to show an ItemStack on hover since it uses some APIs that are not replaceable by spigot's APIs (so it tries to hook into NMS code and it's quite volatile).
If it does please report it to github.

v1.4.2: Set default book fields to prevent invalid tag

Closes #16

v1.4.1

Added length check on book titles

v1.4

Added 1.16.4 support